ground strap on A body to motor??

Here's my basic old car drill. Heavy gauge ground straps, from battery to frame, from frame to engine, from frame to body "for Chebies", heater blower motors to body. Most engines have a small ground strap near the back from either intake or cylinder head to firewall. And corrosion can build up between the bolt and body or cable. Or sometimes people just bolt a ground strap straight to paint. All of these reasons are easily overlooked and become a gremlin. Happens alot with taillights and marker lights that have build up of corrosion, one side is brighter than the other etc..