i had a similar issue with doing the 3g upgrade in my 84 svo mustang it still had the voltage regulator on it
I actually ran a wire into the fuse box and hooked it into the blower motor slot, it went hot in run.
all it does is "excite" the alternator to tell it to start charging
i pulled the regulator off and cut the plug off and wired it all manually
worked good for well over a year now
you may not want to do it that way but i couldnt figure anything else out, not sure if ur car has a blower motor fuse slot tho... ill looka round for the link to my issues i actually had to go to a tbird and cougar site to get the help i needed.
forgot to say i jsut ordered the 3g alt upgrade kit offa some site it came with thew plug for the 3g alternator.