External Voltage Regulator Help

[Tutt]

Hey guys,
Im trying to use a leftover external regulator from my '72 c-10 in my '86 c-30 with a '93 dodge cummins engine. i am using the doge alternator.

the alternator will charge if i put 12v to one field terminal and ground the other field terminal, so i think that the alternator is ok.

with the regulator hooked up, one field terminal has 12v, and the other has 10ish volts. i think that the 10v needs to be closer to ground for the alternator to charge.

i have tried my old regulator and a new regulator, both with the same results.

I am starting to think that the GM regulator and the Dodge alternator wont work together. does anyone have any ideas?