blzr headlights causing quitting

I have a 91 s-10 blazer and with the headlights on for a while the truck dies. It doesn't happen all the time or when i turn them on at that moment, just here or there. when truck dies, i coast to side of road wait till lights come back on and restart. If the lights don't come back on, i cannot restart...I have replaced headlight switch, checked/cleaned/tightened battery connectors, connectors at headlights, grounds for headlights, connector behind alternator. If I don't use headlights, the blzr runs perfect and I also am able to run just the running lights without it dying. What is my next step? Can I run a toggle switch from battery to T/L fuse to keep constant power when using headlights until I figure out what is causing the problem?

I don't know, I see a breaker in the headlamp switch but I can't see in the diagrams where it would shut the motor off. There's a line from the switch that goes to the dash lights so you can dim them but other than a super dead short that kills everything, I don't see anything.
This might be one of those deals where you look at the cost of repair against what the car is worth to you and not some durn book. If it's been a joy to own then a trip to the shop is worth it...heck they might find something about to go and save you another trip.
All help gratefully accepted.

your alternator is probably dying - not produceing enough amps .