tinman

About the camshaft, Ford should feel some guilt about selling them. They are as obselete as a 390. Better to spend your moneys elsewhere.
If you are going top run a carb on that motor I believe you will have to change to distributor.

1979cobra

How large can I go with the cam. The engine I purchased has the GT 40 heads. It is out of a 99 explorer. I want to run the largest cam I can, but I have heard there may be clearance issues.
Please advise.

tinman

Anytime you change any camshaft in any engine you always check valve to piston clearance. About .100" on both the intake valve and the exhaust valve will be fine for a street/strip type car.
How big to run? That's sort of your choice but with the GT40 head I really wouldn't go bigger than about .500" lift, anything more would be a waste of money.
What ever you do, use new valvesprings that are the ones the cam grinder recommends....