Hi, we're a volunteer fire department with a 1982 GMC K2500 brush truck that refuses to crank. I am a Ford person and not well versed with GM products. here's the problem: Turn the key and no crank, all lights dim as they would except when trying to start. 1, Checked the battery and load tested it, it's good. 2, Checked B- from block to Battery, it's good. 3, Took the starter off and bench tested it, it's good 4, Hooked up a test like to starter solenoid circuit and turned the key, no 12v to starter. 5, Traced wire back to firewall, no breaks 6, Went under dash and looked for breaks, could not find any but VERY poor condition. 7, Thought might be a bad ignition switch so we replaced it. 8, Got it back together and still will not crank. I'm stumped!!! Anyone know anything else we can do? It's a 5.7 with a stick shift.