Well I had already done this conversion on my 460 gasser and it worked great.

My stock 65 amp 1g alt on the 7.3 didnt like to power my a/c at a stop light or idleing I was at 12.5v all the time unless I was under way. So I pulled an alt. at the junk yard out of a 90s taurus with the 3.8 which is the 130 amp alt and took the plugs. Switched the pullys to keep the v-belt set up on the 7.3.

Removed the external voltage regulator and cut the wires at the plug. The yellow/white stripe goes to the new y/w on the alt plug. And the green/red goes to the g/r on the plug. Install atleast 4g wire for ground and 12v comming off the alt. to the battery. Tape up the wires that werent used and your good to go. Also disconnect the grounds before starting anything electrical.

The only problem I have is the v-belt pulley is bigger then the stock one on the 3g. So the alt. is turning slower at idle then it normally would so at idle its putting out even less power then it would have with the smaller pulley. This is still more then the 1g though. With lights a/c and the brake I still sit at 14v not 12 anymore. This only cost me $25 and was well worth it.