fun electrical problem

[86 K-10]

i know this will probably be very specific to my truck, but im hoping someone has run into something similar before i go chasing wires. Ever since i've had my truck, i've noticed that the lights will randomly dim at night but i never thought much of it until i installed a stereo in the truck. the stereo cuts off and on when hitting bumps/turning/slowing down. of course i've checked all connections, good ground/power straight from the battery. tonight i noticed that the radio cuts out simutaneously when the headlights dim. the radio will also turn off sometimes when the power window switch is pressed upwards when the window is already completely rolled up. any thoughts?