Rear engined Comp Coupe would be allowed surely if the 4 seater car in question had the motor in that position as its original location.
Here in the UK many club circuit racers have taken advantage of this engine position ruling in what was called the 'special saloon class'. Most racers built were based on spaceframe or monocoque chassis from sports racing cars. Some even had V8 engines and one had the Ford DFV Formula 1 motor.
Various options are the European brands such as Skoda, Volkswagen, Suzuki, Fiat, NSU and the UK brand - Hillman Imp.