Reply to "OEM Rotor and Cap"

There's other considerations with an electronic Duraspark: first will it fit your Pantera? On many Panteras of all years, the clearance between a big-cap Duraspark and the firewall is measured in thousandths of an inch- too close to work effectively.
Usual scenario: you find a cap position that barely fits even if the static advance can't be rotated to quite the correct spot. Drive around town for awhile with no trouble.... until one day, for any reason, you jump on the throttle. The engine shifts on the mounts a tiny bit, the cap touches the firewall and pops up, breaking the rotor. Unless you have a spare cap/rotor aboard, its dead-stop-and-tow-truck-time!
Note- the clearance issue can be addressed in a variety of ways, but there is a less-common small diameter Duraspark cap and accessories made. Both the small and the big Duraspark cap came both with an adapter cone and also as a one-piece cap, further confusing things. The caps take different rotors and spark plug wire ends, too....
Duraspark distributors have many advantages over your dual-point distributor- including accepting the centrifugal weights, springs and internal limiters from your points dizzy to change the advance curve from a 460 truck engine to a performance small-block version. Durasparks still use adjustable vacuum advance cannisters. They accept burn-out-proof e-coils in place of your old can-of-oil coil, and the gear fits cast iron 351-C cams.
But depending on what and where your Duraspark 2 distributor came from, it may or may not be a drop-in, clean-hands adaption. I suggest calling your favorite vendor unless you are intimate with the nuances of 351-C dizzy-swaps.