I think you need to use a different set of headers. For one that looks like a small block, and the spacing on the headers says big block. Two, the exhaust that goes outboard of the frame and then back in for the turbos serves no purpose. Perhaps a Corvette style header that drops straight down, would work out better. I have a set if you need.
As for what body, usually chassis are built after you have a body picked out. However, due to the length of this, I'd go with something longish, like the Revell '39 Chevy Wagonrod, sans fenders.