High Output Alternator Help

If you are staying with Mopar alternators, you need to first, use the "squareback" design rather than "roundback." Also it's not just simply rated output. One of the lower output (I think 47A) has higher LOW RPM output than some of the higher output AKA 55-60A units.

Make certain the belt is not slipping, that the pulleys are not glazed, and THAT THE PULLEYS are proper sized, IE that some "drag racer" has not installed a larger alternator pulley to slow it down

Another thing you can do is get it idling with "everything on" and measure voltage at the battery + with one lead of your meter, and at the alternator output stud with the remaining probe of your meter. This should give a quite low reading and WILL BE THE VOLTAGE DROP of the charging path/ wire from the alternator to the battery.

These girls are well known for voltage drop problems in the bulkhead connector/ ammeter circuit and drop in that line WILL cause additional sag at low RPM

If you insist on "really great" low RPM voltage, you are going to likely have to convert to something like a modern Denso or one off a Dakota/ RAM, etc