alternator upgrade and gauge help

Yep. The weak point in Mopar systems is that they ran the huge charging wire through the bulkhead connector TWICE, the ammeter can develop bad connections, not only just the wire connections but actually IN the ammeter, and in fact the "in harness splice" has failed in a number of cars

Read this article:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

which came from here:

http://www.madelectrical.com/

The simplified diagram shows where PART of voltage drop problems are

What they do NOT show is potential (no pun intended!!) drops in the IGNITION CIRCUIT

In the diagram down the page, find the "welded splice". (This is taped up in the under-dash harness) where it says "to ignition switch". FROM THERE it goes through the switch, out the bulkhead on the dark blue "IGN run" wire

So the voltage drop you can have in the ignition supply buss (follow the diagram) is:

From the battery -- fuse link -- bulkhead connector -- ammeter circuit -- (not shown) -- ignition switch connector -- through the switch -- back out the switch connector -- back out the bulkhead on the dark blue IGN wire

So for higher current situations, ESPECIALLY if you are adding larger stereo, electric pumps, fans, etc,

Bypass the ammeter

Convert to voltmeter

Run relays on the headlights

Run relay for the IGN system / charging system

Run relay for fuel pump

Run relay for cooling fan(s)

If you are not "restore perfect" you can run wiring "straight through" the bulkhead connector for the large conductors, at least.