I don't think I ever saw that 4 bar car. The plans I got, from Don, are a front buggy spring, rear torsion bar car. Older sprinters and lots of the old supers ran that set up, as you know, before going to a 4 bar set up. This plan shows an 86" wheelbase so it was for short tracks not like the Sac. mile. The race you saw Opperman in; was that early 70s when Jimmy Gordon and two other died there that day. I saw several USAC "big car" races there as a kid. The one car you're talking about; does it use double radius rods on both sides? That would have put it in a bind.
Thanks John; on this sprinter the only aluminum I used was the firewall and belly pan; everything else is styrene sheet and tube. I only build these cars in 1/8th scale and I scratch build everything except I buy the spark plug boots and all the bolts. I draw plans for every car I build and I sell a generic set of 1/8 scale sprint car plans if you're interested. It's 11 pages on 12x18 sheets and shows how to build everything even the tires and wheels. E-mail me at firstname.lastname@example.org if you are ever interested.