273 to 318 engine swap info please!!

I have a 67 Dart with the 273 HiPo and 904 automatic, anyone know what would be involved with swapping out the motor to a 84 318? Think the
engine mounts are the same but what about the flywheel, flexplate, and
exhaust manifolds or any other items??? Found a 84 318 engine someone
wants to sell and think that would have the hardened valve seals and such. My 273 HiPo was rebuilt before I got it and is a dog, thinking they
didn't do something right on the rebuild.