May I make a suggestion?
Before the motor goes back in,
gently cut the stock loom off and run your thumb up each wire in the engine bay to check for slits, corrosion, or rodent chewing. If everything looks good, you can get new loom tape and rewrap it. Also, there's another member here named
@crackedback that sells a bypass kit for the ammeter.
It's cheap insurance if you're going to keep the stock harness. I would highly recommend at least looking into it.
I almost lost my old 70' Nova to a 12v constant wire that was shorting against the metal dashboard. It caught the insulation on fire when we were driving it. Thank God I brought an extinguisher with us that day. Ever since then, I've been somewhat neurotic about wiring and promote risk management with electrical.