If none of your wiring has been upgraded and none of the bypass fixes for the bulkhead connector have been done, then everything electrical slowing at idle is what can be expected and believe it or not pretty normal for an older Mopar.
The MAD bypass for the charging system and bulkhead, plus a relay kit for your headlights will make a huge difference in those area's.
There are also some alternator upgrades available like Denso versions, as well as regulator wiring upgrades that can be done.
Part of the problem with these old girls is that all those higher amp loads run through many feet of what I see as undersized wires before the power ever gets to where it needs to go.
Like I said, taking high draw loads like headlights and charging system off the factory wiring helps a ton.
I use a lot of LED's replacements also, because they use a TON less electrical load.
An example:
When you turn on your headlights the power supply for them comes from the battery, down through the fusible link, across the amp meter, over to the headlight switch, back down through the dash harness to the hi/low beam switch and through another 10 feet of wire to the headlight.
This is a HUGE draw before the power ever even gets to the bulb filament.
All those connections, switches and everything have to carry all the load to light the bulb.
With a headlight relay kit from our member Crackedback the switches and all that dash harness wire, switches terminals and such are relieved of that huge draw and related loss of amps along the way.
After that one upgrade there is no big amp draw on the harness, connectors and switches any longer, as all that is now carried by the relays in the kit, and all your existing stuff has to do is activate the relay.
This is a HUGE load off your existing wiring and switches, so they last WAY longer without that wear and tear.
That leaves a bunch of amps left over for things like signals, wipers and blower motor.
My car has a relay kit, a rewired charging system (MAD type bypass) and LED interior dash and gauges, brake/tail/turn lighting, so at a stop with the headlights, brakelights, a signal, wipers, heater and stereo going my lights don't dim at idle and the signals and heater don't slow, and I still have the original type alternator and charging system.
One other easy one is to change to an electronic flasher unit, as they keep a steady flash speed because they don't rely on load to flash.
This is just some examples of what cause and how to solve the problem you asked about.
Dying when you let off the gas could be anything from idle speed adjustment to plugged up idle circuit in the carb.
A simple one for the idle circuit is to screw the mixture screws in until they stop counting how many turns it takes.
Remove them, shoot a shot od WD40 in each hole and hit each one with compressed air, put the screws all the way in and count the turns backing them out so they are about where they were.
It takes about the same amount of time that it took to type it, and could very well solve your problem.
