As another option, there is an alternative way to adapt or integrate those Pentroof valvecovers to your car, but it's costly, and worth it:
Step 1: remove 351 engine
Step 2: install Ford FE 352 to 428 family engine, with correct FE heads.
Step 3: install pentroof valvecovers on to FE engine.
Just kidding. Ha, Ha.
Duane