4V & all
The SMP p.n. AL-482 cap is designed for an International Harvester distributor made by Prestolite. The cap does indeed fit the Motorcraft distributor, although the locating method is a little flakey; i.e. a slot in the cap uses a vacuum advance screw as a locating tab. I have a NOS distributor in which the screw head is the right size and makes a nice snug fit. But I also have a rebuilt distributor in which the head of the vacuum advance screw is smaller, so the cap's location is not as secure, it has wiggle room.
The complementary rotor for the International Harvester cap, SMP p.n. AL-171 DOES NOT FIT the Motorcraft distributor. I've been meaning to check and see if the Ford small cap rotor (SMP p.n. FD-115) will work, just haven't done it yet. Until somebody figures out which rotor (if any) will work, I'd recommend the following parts:
4 inch diameter distributor cap with female terminals for 1976 breakerless ignitions SMP p.n. FD-149
Complementary rotor for the 4 inch diameter distributor cap SMP p.n. FD-115
1976 ignition wire set for the distributor cap with female terminals SMP p.n. 7815
(note: Ford began using the 5 inch diameter cap in 1977)
The small cap is 4 inches diameter, the big cap is 5 inches diameter, so using the small cap gives 1/2 inch additional clearance. It might be helpful if we knew the chassis numbers of the Panteras that can't use the larger cap. Are they all Pre-L? Or are the issues intake manifold clearance like Doug mentioned?