My '71 C10 was grounded to the passenger's side head. That is good, as far as it goes, but I felt that additional grounding was needed, so I dropped a #4 cable from the block to a bolt hole in the frame. Then I added an 8 gauge ground to the right inner fender. I made sure that connection points were clean and shiny and used star washers as well. I didn't use but one ground in the rear to the bed. Be sure to add a heavy 6 or 8 gauge ground from the frame to the cab as well.
On my truck, every previous owner must have thought he was God's gift to wiring because I have a couple boxes worth of Scotch locks and butt splice crimp ons that I removed.
I rewired everything from the harness plug on the drivers side in back and that and the new grounds made all the difference in the world! Solder and heatshrink are your friends!
I also switched to a 10SI alternator with internal regulator at the same time I did the other rewiring. If you haven't done this, it is well worth your time and important if you are also switching to HEI as I am.
Best wishes, Les
