Originally, I had Modified Gas Roadster on the brain (any type frame allowed), so when I had the chance at the truck, I envisioned the 1968 Chevy SWB frame I have as a starting point. Newer frame, trailing arms, factory IFS and a wider main rail arrangement making it easier to mount a cage.
It would seem to me that the frame should be the best/strongest design available, within each competitors budget, for safety reasons. As long as the body panels and bumpers remain in the same relation to each other, the total frontal area and cd would remain the same, and that is the real hinderance or challenge to going fast. Making an old brick cut through the wind as efficiently is possible.
The frame just holds it all together. In a spin-out, roll or other sudden stoppage, I would rather have something more modern than 2 C-shaped pieces of 63 year old steel, in a narrow ladder arrangement, supporting my cage.
Maybe I shouldn't worry about it, like RichFox said, it is highly unlikely I will ever be in the impound. This is for fun and the experience, and while SCTA rules are the primary concern with this build, it will also see the Texas Mile and maybe one of the local 1/8th mile 'strips, after a 3rd member swap.
C. J.