Conversion Kits

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.

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.

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 interest