I've built several dirt track race car frames from the ground up, starting with a street vehicle frame and doing major modifications. There's one rule of thumb on race frames- - - -build it three times as strong as you think it needs to be, and don't be too surprised if it breaks.
"Strong" doesn't necessarily mean "heavy". A truss structure built out of thinwall tube can be as strong as, or stronger than a heavily fish-plated assembly if it's designed correctly. Just make sure your welds are the correct alloy, done with the right heat setting on the welder.
One upcoming project is going to be fitting a later-model 3/4 ton Chevy IFS to my 59 Burb. It's going to need some frame reinforcement and crossmember fabrication in places, because I'm also planning to go with a 500 Cad engine/Turbo 400 trans at the same time. The suspension stress points and torque application areas will be entirely different than the 283/3-speed it had originally.
Jerry
