I have a 91 pickup 22re and when driving at night with the lights and heat on my voltage drops a little under half way and my radio will cut off, the headlights and dash lights dim and the heat barely blows warm air but the truck will still run but once I turn it off I have to wait several hours/next morning for it to start back up unless I jump it. Are these signs of a dying alternator or bad voltage regulator or something else?

 

Time to get a Multi Meter get some real voltage numbers

It could be any number of things

Charging system problems need to be looked at one step at a time.

Corroded or loose battery terminals

Corroded or worn connections in the battery cables. Bad grounds will cause all sorts of issues

Even a loose belt

Don`t blame a bad alternator till every thing else is checked out.