There is a current 1/12 scale GT40 Mk II available as a glue kit as most of you know. That could be a source for drivetrain and suspension parts swapping as well as wheels and tires. The kit sells for around $180.00 on the net. Be care full on your choice of scale as most RC cars are 10th scale. Doing a mold and popping out resin cast bodies is very do-able. There are "many" resin cast scale body makers across the USA already. Most have excellent quality products available in the standard model scales of 1/24, 1/24, 1/32, and 1/43. If there is a demand for these in a moderate number someone will step up to the plate. I paid $50.00 for a 65 Daytona Type"65" Coupe (supercoupe) resin body in 1/25 scale, with interior inner panels and floor pan, tail lamps and gas caps, clear windows. quality was 9.75 out of 10.0....................................just another $.02
Maybe an option. CNC wood. you can get a nice piece of hickory or other and make it out of a solid piece and CNC it down. Machine time should be quick. Clean up time for the CNC for wood shavings, hmmm. Then sand it a bit and some poly on it, could be really nice.