1986 GMC Sierra wire harness

[fang508]

I am having trouble finding out which port under the hood is bat+ so I can test all the electronics. My fusebox has a terminal side that goes through and protrudes under the hood that isn't labeled or anything. All diagrams I find only correspond to the under dash fuse box. This used to be a diesel so there is quite a few other connections that go nowhere since this was a diesel to gas carb swap. Also, while I was digging under the dash I found a grey plastic box that says "voltage regulator". It was just hanging there. Can I take it out or should I just leave it for now? The P/O really messed around with this truck..