I'd love to follow this thread----------Dave, first thing is to check the rules of the class that you would want to race in because I think more of them that allow DOM also require 1 3/4 od and thicker wall than 4130 moly which can be 1 5/8 x .083?????????

The main rails for a street driven gasser would be a lot easier to build with the 2x3 tubing as far as mounting brackets,etc--------also there are lots of places that you can get rails bent for various cars so you just need to add the cage in round tube.