Schumacher manuals are easy, pdf files are listed at the top of the page.
Original CAT
http://www.retromodelisme.com/manuel...chumacher.html
CAT XL
http://www.retromodelisme.com/manuel...chumacher.html
Procat
http://www.retromodelisme.com/manuel...chumacher.html
If the body is wide it's likely to be the Parma body for the Cat. Kamtec are producing repro XLS and Procat bodies and undertrays, and there might be another alternative in the near future producing the wing, belt covers, etc.
And I've also got a CAT with the Corally alloy chassis, just mine doesn't have any battery trays