dies going down road.. electrical problem

i have 78 dodge ram d-100 and when i drive down the road it will just die like the battery is dead.. the battery, alternator, regulator, ignition module, ignition resistor are all new.. it mostly happens at night when the head lights are on.. when it sits for a few days, and i start it the battery is dead, have switched out batteries, still the same.. need help

Seems like I read about a headlight switch and a voltmeter issue about a year ago. Does the headlight switch get real hot? How about the area behind the voltmeter up under the dash?

yeah it sometimes get hot.. so does the big red wire the positive supply wire that goes into the fuse box, it sometimes gets hot..

found the short in the truck!