Fixing grounding problems is like eating an elephant- - - - -"one bite at a time!" Concentrate on one specific circuit, fix it, and move on to the next one. Rusty body metal does not make for good grounds- - - -run ground wires from the frame and/or engine block to all the sheet metal components; fenders, cab, bed, etc. There's no such thing as "too many grounds"!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!