Wouldn't it be better just to try and contact the builders (if they are still around in some guise) with the chassis number to confirm it's authenticity ?
Would ford have a record of the car being supplied to Rouse to be built or was it just something some people did independently of Ford once they had bought their 'standard' Cosworths..
There are plenty of people on here who will give you a good steer, unless someone has all the info to hand in which case you're all set, but surely the only way to be sure is to talk to the people who built it with the chassis number.. anyone can fit rouse parts to a standard car..
2p..