La 318 mount don't fit 5.9 magnum.

krazykuda said
He has the later "biscuit" mounts, the 72 and earlier cars take the "sandwich" mount that you are referring to.

Here's the 340/360 repro sandwich mounts:

Engine Conversion and Replacement Kit

Dang! Those are nice! Unfortunately not in the budget. Gonna try to weld a tab up. Maybe down the road. Thanks for the knowledge as well. Been learning something new everyday with this car!