Rebuild or replace?

Personally, and just my opinion. Magnum. Either or. Odds are can pick up a good motor for around the same price as a 318 or 360 core. I'm not sure of all the details of what has to be swapped, I know intake, distributor, if you want v belts the timing cover and pulleys. But you have all that, other than intake. Unless you get lucky with a 318/360 core and find one with very little ridge, you are up to having to have it bored and honed, new pistons and rings. Go to junkyard, get a 5.2/5.9, just about guaranteed not to have any ridge, pistons and rings still in good shape, can hone and change rings for peace of mind if wanted... But new bearings and timing chain, like $200 or so for the intake, use the timing cover and pulleys you have, carb? And distributor you have and call it a day. Take it easy until you get the rearend upgraded. Oh, you will need a flexplate balanced for the engine as well, at least for the 5.9... Again, just my 2 cents