Strange electrical issues with my '72 Dodge truck

I've had this truck a few years now and when I first got it I removed quite a bit of add-on wiring that previous owners had put in, I assume for powering stuff in their camper as that's what this truck spent most of its life as. One issue I still have though is if I go to crank the engine with the headlights on it instantly blows the fuse for the instrument panel lights. Every time I drive at night I have to make sure to start the engine BEFORE turning on the headlights or my gauge lights go out and I have to fish around for yet another fuse. I've also noticed at night when the engine is running the turn signal lights in the gauge cluster flicker very dimly (can only be seen in darkness/at night). What the heck could cause this? Btw I converted all the bulbs in my instrument cluster to LEDs and they themselves all work fine.

Not sure if it's related but I am planning to replace the alternator soon as the bearings are pretty noisy and as far as I can tell it's original or just very very old. Some of the wires coming off the alternator are also not in great shape and I plan to cut back the wires and re-splice new connectors on the ends. Any and all advice is appreciated.

OH and one more thing, apparently it's a common issue for the main power feed wire going through the ignition switch connectors (located under the steering column) to overheat and melt/blow out, one of the first repairs I had to do on this truck was a new ignition switch and new connectors for the bigger wires. Supposedly the main cause is too much current draw from the heater blower motor so I always keep it on Low or Medium fan speed, haven't gotten around to putting it on a separate circuit as the fan blows plenty of air on the lower speeds.

I did go through and redo all the grounds I could find between the engine, frame and cab.