Electrical Help Please

OK so you're saying that the alternator and voltage regulator should both be good? And am I to infer since you didn't mention the battery that you think it is the issue?

I don't know which starter is on the engine. Looking at an FSM, older Chrysler starter will draw around 180 amps from a higher compression v-8.
The new Denso starters many use may draw less.
1706479019671.png

My point here is that you can use your starter as test load like I suggested earlier. Start with a fully charged battery and the votlage it drops to during the start will give you a ballpark idea of its internal condition.