AP is an SCCA class. 427 vette's Cobra's the 904 Porsche probably because it was mid engine were in that class
Does it have a roll bar? If so look for a stamped number or tag. All the cars I have had that ran in SCCA or the Trans Am series had stamps .
Start searching for programs from Riverside races or whatever tracks you think the car was at...
Here is a good site for Riverside stuff
http://www.sportslinkup.com/shop/0-R...raceway-1.html