First---Thank you Brent. I intend to use all new parts in a build I'm planning, and had intended that such things as pumps, lines, etc. would be compatible. My concern was that I might have missed something. All is well.
In regard to headers fitting with the eight-bolt exhaust pattern, when I put a 427 in my '67 Cougar in '69, (if I've counted on my fingers correctly), I bought headers for a 390 Cougar and replaced the flanges, to fit. They were no picnic to work on, requiring raising the front of the engine until the bell-housing hit the firewall, and then removing the motormount on the passenger side for hand-room enough to get a wrench in place. I put the engine in with the driver's side all bolted up tight. It is all do-able. Good luck!
KS
