A-body GM cars are body-on-frame. Decades ago it was trick to swap in a convertible frame, because it was boxed, while the sedan or coupe frame was a C-channel. This was like the early '70s.

Even though the body won't wrinkle like a Mopar, it will still have quite a bit of twist from being tied to a twisting frame. I'd say some chassis work, like a roll cage, would be a good investment.

The rear end WILL bend, that's why most all 9" rears have braces welded in. The axles are suspect, as is the differential housing. 35 spline axles and a way stiffer and stronger case should be on the menu. Looking around, I see that Yukon makes both a nodular iron and a bolt-through aluminum case, also an aluminum Dayton pinion support.

As mentioned above, all this strength will be needed if you get the car to hook.

R.