Should I bore a 74 318 to 340 ci or just go with a 360?

I don't think you can bore a 318 to 340! the walls would be super thin and would over heat. You Could Bore a Polly 318 to a 340 cause thay have thicker walls. but you can never go wrong with a 360.

Some of them will go that far. You have to have them sonic checked first.