What do I need

You can make your 318 mount brackets work

You'll either have to get a different torque converter weighted for a 360, or (the easier) is to buy a B&M aftermarket flex plate which is weighted for the engine. Be careful it's for a 360LA, not a magnum, or cast crank 340.

Pretty much everything else should bolt in. You'll have to use your old 318 manifolds, which are not the best. Depending on what you have (power steering, etc) you probably will want to use the 318 pulley set up.