You might also find someone at
http://www.classracer.com with old rulebooks and likely others with "parked" MP cars. MP was one of my favorite classes in the late 60's early 70's. Mid 70's(75?) A/SM was pretty cool too.
Somewhere I have a 1975 SuperStock magazine with the first set of rules for A/SM in it. IIRC I think the cube limit was 366 but cant recall the weight break.
BTW Creating a series you will need sponsors. The racers and tracks are out there and easier to obtain.