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Billy's Speed Shop
Conversion Kits
Complete, matched powertrain conversion kits engineered for specific vehicles. Every major system defined, supplied, and ready to install with nothing left to source.
Genuinely complete
Engine, gearbox, wiring, fuel, cooling, exhaust, instruments, and every fitting. Nothing left to source.
Engineered per vehicle
Each kit is developed on a physical build for a specific chassis, not assembled from catalogue guesswork.
UK stocked and shipped
All brand new parts from Chevrolet Performance, Holley, Lokar, and more. Shipped from the UK with support.
Why a complete conversion kit changes the outcome of your build
Most engine conversions fail, or stall, not because the engine or gearbox is wrong, but because the supporting systems were never properly defined. Builders spend weeks chasing individual parts, cross-referencing fitment across forums, ordering components that look right on paper but clash in practice, and then troubleshooting pressure drops, wiring conflicts, and clearance issues that could have been avoided entirely.
The result is a conversion that takes twice as long, costs more than planned, and still leaves the builder unsure whether the fuel system will hold pressure, the wiring harness is mapped correctly, or the cooling system is adequate for UK conditions. The engine and gearbox are the easy part. It is everything around them that determines whether a conversion actually works.
A complete conversion kit eliminates this. Every system is defined in advance, matched to the target vehicle, and supplied as a coherent package. The engine management talks to the transmission. The fuel system is plumbed from tank to rail with the correct pressure, fittings, and hose. The cooling system fits the chassis. The adaptor is engineered for the specific transfer case or bellhousing. There is nothing left to source, fabricate, or guess.
How Billy's Speed Shop develops a conversion kit
Each kit starts with a real build. We do not catalogue-engineer conversion kits from spec sheets. We develop them by working through the installation on a physical vehicle, identifying every interface, clearance constraint, and system dependency, and then selecting the correct component for each requirement.
Vehicle-specific engineering
Every kit is developed for a named platform: Defender Puma, Cobra replica, Ultima GTR, or a defined LS swap target. We address the specific clearance, wiring, and drivetrain challenges of that chassis, not generic LS swap advice.
Complete system scope
Kits include the full powertrain, electronic management, fuel and air intake, cooling, exhaust interface, cabin controls, instrumentation, and ancillaries. No partial kits, no "you'll also need…" surprises.
Brand new, globally supported parts
Every component is brand new from manufacturers like Chevrolet Performance, Holley, Dakota Digital, Lokar, Hooker, and AEM. No secondhand gambles. Full manufacturer warranty. Global parts availability for long-term ownership.
UK supply and support
Kits are stocked and shipped from the UK. Right-hand drive considerations are addressed where applicable. Support is available for builders and workshops throughout the installation process.
What every conversion kit includes
The specific components vary by vehicle, but every kit we develop covers the same core systems. This is what separates a complete kit from a crate engine and a box of parts.
Engine
Factory-fresh crate engine with intake, throttle body, injectors, fuel rails, coils, and break-in essentials. Multiple power levels where available.
Transmission
Matched automatic or manual gearbox with correct converter or flywheel. Calibrated for the engine output and vehicle weight.
Adaptor & mounts
Vehicle-specific adaptor housing linking the GM powertrain to the existing drivetrain. Engine, gearbox, and transfer case mounts engineered for the chassis.
Engine management
Factory-grade ECU managing fuel, spark, and transmission shift strategy. Pre-configured for the engine spec with OBD-II diagnostics.
Fuel & air intake
Complete conversion from original fuelling to EFI petrol: air intake, in-tank pump, filter/regulator, full AN plumbing, and every fitting required from tank to fuel rail.
Cooling
Radiator, hose routing, and fittings selected for the engine bay dimensions and thermal demands of the vehicle. Oil cooling where required.
Exhaust interface
Manifolds or headers selected for clearance within the specific chassis. Oxygen sensor provisions and outlets ready for custom fabrication.
Cabin controls & instruments
Shifter, cable, and gating for the transmission. Gauge cluster with CAN/OBD bridge for live engine data on real analog or digital instruments.
Ancillaries
Accessory drive, alternator, power steering, A/C provision, starter motor, and finishing hardware to complete the installation.
Available now
Featured Conversion Kit
Defender 90 & 110 Puma: LS3 & 6L80
Chevrolet Performance LS3 6.2L V8 & 6L80 6-speed automatic
The most comprehensive Defender LS conversion kit available in the UK. Engineered specifically for right-hand drive Puma models, retaining the LT230 transfer case and full permanent four-wheel drive. Supplied as nine modular packages covering the complete powertrain, all supporting systems, and every piece of installation hardware.
This kit replaces the Puma diesel with a modern LS3 V8 producing 430 to 525 bhp, paired with a GM 6L80 six-speed automatic with adaptive shift strategy. The result is a Defender that tows, tours, and overtakes with confidence, while remaining mechanically straightforward and globally serviceable.
430–525 bhp
6L80 6-speed auto
LT230 4×4 retained
UK RHD
9 packages
Brand new parts
Kits in development
We develop conversion kits based on real demand from UK builders and workshops. The platforms below are in active development, and each follows the same methodology as the Defender kit, starting with a physical build and working through every system interface before the kit is released.
Register your interest on any kit below and we will notify you when it becomes available. Early registrations also help us prioritise development order.
Coming soon
Cobra Replica
AC Cobra / Dax / Gardner Douglas / AK Sportscars
LS-based powertrain conversion kits for cobra replica chassis. The LS platform is an increasingly popular choice for replica builders seeking reliable, tuneable power with strong aftermarket support and compact dimensions that suit the cobra engine bay.
This kit will cover engine, transmission, wiring, fuel delivery, cooling, and ancillary systems, all matched to the dimensions and mounting conventions of common UK cobra replica platforms including Dax, Gardner Douglas, and AK Sportscars.
Register interest
Coming soon
Ultima GTR / Can-Am
LS & LT high-performance powertrain packages
High-performance conversion packages for Ultima platforms. The Ultima GTR and Can-Am are designed around the Chevrolet LS and LT architecture, making them natural candidates for defined powertrain kits that remove sourcing complexity and ensure component compatibility from the outset.
Kit scope will include engine, transaxle or transmission interface, engine management, fuel system, cooling, and wiring, all specified for the performance envelope and packaging constraints of the Ultima chassis.
Register interest
Coming soon
LS Swap Kits: Universal & Platform-Specific
Engine, transmission, wiring, and fuel packages for common LS swap targets
Not every conversion requires a vehicle-specific kit. For platforms where the swap is well-established but the parts sourcing remains fragmented, we are developing universal and semi-universal LS swap packages that bundle the engine, transmission, wiring, fuel system, and ancillaries into a single, tested order.
These kits will be aimed at builders who know what they are doing mechanically but want to remove the weeks of parts-chasing, cross-referencing, and compatibility troubleshooting that comes with sourcing an LS swap piecemeal. Platforms under consideration include classic British sports cars, kit cars, and popular European and Japanese chassis.
Register interestBuilding something that's not listed?
We develop new conversion kits based on demand from UK builders and workshops. If you are planning a conversion and want to discuss whether a kit is available or in development for your platform, get in touch. If you already know which engine or transmission you need, you can browse our full catalogue of crate engines and transmissions.