[Wgesnerjr]

I have the same questions about the ground straps. My truck came to me with no engine in it, so I have no idea what was stock. For all my investigations, This is what I have determined. Take them for what they're worth.

1. Negative batt cable. Goes from battery to engine. Where, I don't know. If its like all other Chevys, i suppose it goes to the alternator bracket. Also has a pigtail that goes to the core support.
2. Ground strap. Goes from firewall near the a/c box to the engine. (I guess. Again, no engine)
3. Ground strap. From bed to frame. On the underside near the front passenger corner of the bed. Actually saw this one in place!
4. Ground strap??? There appears to be a spot for a ground strap on the frame below the drivers door. However, it is missing on my truck. Looks like there was one at one time and it is outlined by dirt, but is not there on my truck. Could be stock, could be aftermarket, who knows?

Not sure how the frame gets a ground since the engine, cab and core support are all in rubber mounts..but it is grounded so it happens somehow.

I would also check for loose connections at the battery, alternator, starter and firewall bulk head connector. If you wiggle any of these and see lights get brighter or weird things happen, that might be your problem.

I once had an old Catalina that had electrical problems and slow starts. Turns out it was a loose main battery cable at the starter. I was leaving work and started my car when someone saw sparks coming from the underside. It was pretty scary to watch. Tightened it up and solved my issue. Just a thought.

Let us know how it goes.