I knew people that raced the old 6s, and they used quite a few V8 parts on them. If they used the truck engine for a basic casing then they will bore waaay out. Red Andrews ran one that was like 305 Cu.In. This was in the 60s tho. Altho I do remember Red's car having a 68 Mustang stock car body welded into one piece and bolted on for a "Run What Ya Brung" 1/4 mile dirt race. He just drove around the Hemis, 440s and 427s with his little 6 riding in a frame from a 32 coupe with a stock front axle transverse rear spring with an early 4-link in the rear and a cage that wouldn't pass tech for a 1/8 mile drag strip today. Ah, the good old days. How did we survive them?