A different alternator question

Hopefully this is a different question. The issue, poor charging at idle. 12.6 without a load. Discharge with a load. Verified grounds, and voltage drops.I've looked at all the Toyota, Ford, and Dakota alternator conversions.
Why do one of these, instead of a Powermaster alternator?
If choosing a Powermaster, would you prefer a 1wire Chrysler style, or 3 wire Chrysler style, square backs?