If the body is good I would build it. The interior (seats, door panels etc.) from any mid size gm from 64-65 will fit and even 66-67 with some mods. For Chevy, You will need Chevelle V-8 frame mounts. Then everything will bolt in. The original trans for these cars is a Muncie, not a Borg-Warner. The 300 engine has little available for speed equipment. The ten bolt rear will probably be the weak link. But, even that can be worked out.