Good luck with restoration mate. I will keep an eye on the RC swap.
I have no guide since it was such a big learning curve for me so can only offer some advice.
Install an aftermarket ECU... eliminates AFM, Injector resistor packs, stock ignitor and associated wires / plugs.
If you are not comfortable in wiring up an aftermarket ECU then recommend you do not attempt a wire tuck on a GT4.
Arm yourself with all the wire diagrams you can download., Print them out and sticky tape them together as a map and learn to read them.
GOLDEN RULE: If I did not know what it is for then I cannot cut it until identified. TAG EVERYTHING you cut.
My wire layout is basically this:
Injectors, distributor and TPS wires between intake manifold runners and through stock hole in firewall connected to ECU.
ABS, Alternator, headlights, thermo fans, blinkers, boost solenoid inside guards, re connecting to main fuse box located in glove box and re distribute from box to battery / starter motor & kick panel = interior power.
Starter motor, speed sensor, reverse light switch through stock hole in passenger footwell connecting to main fuse box, kick panel for reverse light & dashboard for speed sensor.
Lots of sorting, cutting, extending and reconnecting. Make sure you use the same gauge wires when extending and solid joins.
I re wired a lot of the interior which was a painful :bangshead: ... leave it alone :crazy:
Stay focused when tracing wires, its a maze that can be daunting. Many wires loop onto themselves, split into plugs and change color.
The DBA's are aftermarket items for Mitsubishi Evo 7/8/9. The Evo and Audi S8 were only available in 32mm thickness at the time so not sure if that has changed.
No compatible hats as you saw.... STi WRX ones you might get away with but the offset again will cause problems.
I ended up learning CAD and milled out a custom set. Below are pics of the brake setup coming together.