need some input on a budget 318 build

If the engine is going in the fish in the background in your avatar, I hope you've considered the problems of running dual exhausts on a 60-66 A-body. The rear TB crossmember is only notched on the drivers' side. Of course you can run a pipe under the crossmember on the passenger side, but it is very vulnerable to being crushed.

I've seen some ½-fast solutions to this. In my mind, however, the slickest was a fellow who used a Y, 3" pipes, and a race muffler single exhaust. If sounded fabulous. You may have TÜV issues with that particular setup, but you get the idea.

Many good memories of South Germany courtesy of Uncle Sam. Best of luck to you with the project.