318 or 360?

So for the 360 I would of course need motor mounts (which are hard to find )..... BTW it is a 74 Dart its going in.
What is the big difference between the early LA 360 and a Magnum? or even a crate 360?

the 318 I can get comes with the trans and rear and driveshaft..
The 318 mounts are available...not sure what headers I would need and Im pretty sure a muffler shop would have to build me an exhaust system????/

All this info is helpful indeed So all input is appreciated.

if I were to take it to the track I would hope to run high 13's possible with the 318?
In Order....