I had a bunch of Mopar NASCAR chassis pictures in my B body performance book. Basically the Mopar chassis evolved as NASCAR evolved. In the late '60s they were using torsion bar suspensions with rear leaf springs but year after year the chassis designs became stronger and more sophisticated. The K frames got moved up and welded to the chassis rather than bolted on from below. The torsion bars lasted a few years but eventually gave way to coil springs. Same with the rear leaf springs. They hung in there for a bit but then gave way to the long swing arm truck rear suspension that everyone eventually moved to.

I poked around some old NASCAR and sportsman cars when I shot pictures for the book. It was interesting to see how they kept moving weight around and making things stronger. The battery box moved a bunch of times, they went from single shocks to dual shocks up front, moved from drum brakes to disc brakes, etc. They used the C body front knuckle for many years then eventually moved to an aftermarket design.