Same as I said in my prior post. Has to be period correct. Look at Hewland gear boxes. They still make the housing and parts for 40+ year old gear boxes...
Best to go to a race weekend and talk to the racers and tech Stewarts. Most of the time the tech Stewart’s are racers or car builders and will have the answers to your questions about the rules depending on class. Most of the time in vintage racing, the car must be presented as they were back in the day, but safety equipment is current. Cages, seats, etc. also, last summer, I helped my brother assemble a 1975 Ralt RT1 formula Atlantic. The tub (chassis, cockpit) was built in, wait for it...
March / April of 2020... a full copy of the prior tub, which is pieces and kept. The car is presented as it was back in the day..
