The magnum is out of a jeep? Before doing anything else, make sure the starter is in the same place as your current engine... I want to say jeep put it somewhere else...
the starter pocket is on the trans bellhousing, engine itself is the same.
also for questions about the crank, the 318 Magnums used the same crank as every other 318 at least back to 1968.
some were drilled for a pilot bearing, some not. There is a needle bearing you can get to go in the torque converter pilot hole so no worries if your crank isn't finish-machined for the pilot bearing.
