Reply to "aluminum heads"

To answer your question, as received 40+ years ago, the Pantera's 351-C had iron 4V heads with very large ports and valves. 2V cylinder heads have smaller valves and intake & exhaust ports than 4-V heads. This will affect which intake manifold and exhaust headers that will fit the new heads.
Having said that, be aware that ALL original 1970-design iron heads had too-big intakes and poorly designed exhausts compared to all current aluminum heads available. You'll get more power, better driveability and slightly better mileage from any modern heads, and a single person can remove and install an aluminum head on an engine while it's in the car. Each aluminum head will be some 30 lbs LIGHTER than an original cast iron head, which makes quite a difference in muscle-strain when you're working on your engine by yourself.
But make no mistake- it is NOT a matter of simply removing your iron heads and bolting on a pair of aluminum ones; most of the parts from your iron heads will not fit, and those few that do fit are not recommended for re-use. Consult with a Ford Cleveland shop or a Pantera parts vendor for details if you're not intimately familiar with these engines.