You will need to swap the oil pan from the 273 onto the 318, and the bottom radiator hose will be on the wrong side on the 318. Your motor mounts off the 273 will work right back on the 318. You will need to get some 1/4 inch pipe plugs to screw into the air bleed holes under the exhaust ports on the 318, or you will have an exhaust leak. That's about all I can remember. You may have other minor things, but those are the biggies. Nothing that can't be fixed with a little work. Good luck.
