How do I perform an all-wheel drive conversion on a Mazda RX-7 FD?

There is no bolt-on or documented way to convert a Mazda RX-7 FD to all-wheel drive: Mazda never produced a factory AWD RX-7, and because the FD's chassis and drivetrain layout are completely different from earlier RX-7 generations, an AWD conversion would have to be a purely custom, expert-level fabrication project with a completely bespoke drivetrain solution.

Historically, only highly customized, expert-level race vehicles have used AWD RX-7 platforms, such as Rod Millen's 2nd-generation (S4) Pikes Peak car and a 1st-generation (S2) build that utilized front-wheel drive Mazda 626 components ⁸.

For those older 1st-generation RX-7s, the custom conversion involved heavy fabrication, using a 4WD Mazda B-Series (B2xxx) middle differential and the front transaxle from a Mazda 626, requiring a significant financial investment ⁸. Those specific parts and methods do not directly apply to the FD, however, given its different chassis and drivetrain layout.