ZL-1 H.O.;
The 1970 P&A shows 3955707 as:
1966 Chevelle (S.S.) w/H.D. Susp. (2nd design) (max. load 2718 lbs.) I need to double-check this. It might be a typo.
Which is interesting since 3955707 is a 1970 AMA Specifications spring for the at least the Nova. Are you sure that your car was not a late 69 built car instead of 68? The 1969 Camaros ran over into normal 1970 production dates. They started using the 1970 paint colors on the late 1969 Camaros where the colors were similar.
The late build cars might have received updated components. This might be especially true of springs. In 1969 and 1970 they were computer selected based on the options on the car.
So if you car is a late 1969 built Camaro (09D 1969) then it is possible that you got a 1970 model spring. If you car is a 1968 built Camaro (1968 09D) then I would suspect a spring swap with a Nova.
Do me a favor and used one of the 1969 Camaro Spring Calculators found on my web site. Let me know what spring it selected for you.
1969 Camaro 12437 Z28 Spring Decoder
1969 Camaro 12437 L34 L35 L78 Spring Decoder
1969 Camaro 12437 L48 L65 Spring Decoder
Thanks,
Greg