Oh gosh, I removed my factory voltage regulator over ten years ago when I upgraded to 3G on my 84 5.0L and used the internal regulator on the 3G instead.
Perhaps contact that company that always advertises 3G and alternator upgrades in the magizines and see if they have converter wiring.
I'd literally have to go unwrap my wiring (buried inside that 342 stroker, headers) engine area to tell what the colors matched up to now.
But the good news it's an easy thing to do (I know because I did it way back then with no help!).