360 magnum

Todlich nailed it...read the magnum swap site...

Correct weighted flexplate to run a neutral balancer
360 type engine mounts or modify yours
360 LA A body oil pan and correct gaskets
Cam extension snout (works, but machining required) LA roller cam (if you want to run LA front dress) or magnum front dress with electric fuel pump...depends on what you wanna do...
magnum intake-if you go carb
LA distributor if you go carb-magnum is a locked out unit

...search function on here-there are probably a few dozen folks who've done the 5.2 or 5.9 magnum swap, myself included. I wish I'd found a 5.9, but a 5.2 was given to me, so that's what I went with.