273 mild build-----

If it is a 67 or later, the air gap should fit but there will be a manifold to port mismatch. You might be better off with a small port 318 intake to increase port velocity. You also might check into Doug's headers which are essentially the same design as TTIs but without the stepped pipes and are much cheaper. For a mild build I would consider Comp Cams XE256H or XE262H