318 complete combo suggestions...

If you really take 6-8 trips highway trips think about what rpm you want to live with
before picking rear/tire size/trans combo, that adds up $$$ . If you are going to have to buy an intake might as well get an aluminum saves a lot off weight. Small cam 210-215 @ .050 read up on all the flat tappet cam/lifter failures and choose carefully, break in procedure
and oil critical. Clean up the heads,better springs, Mr. Gasket .028 head gaskets.
All other suggestions above make sense IMO.

He won't have to worry about lobe failures with a Magnum. ;)