Adding my own electrical issue to the mix

[rgunlock]

I am wrapping up restoration of my '78 K15 and trying to work out the kinks. After a weekend of sitting, the truck didn't have enough power to crank but still had lights. Next morning, not even the lights. I'd driven it that Friday and all was fine. This truck has a brand new battery and has been completely rewired with an AAW harness. I have added a few aftermarket goodies as well. Best I can tell, everything electrical on the truck is working fine other than the lighter.

So I read a bunch of threads here concerning various electrical issues and last weekend went out and pulled the positive battery cable off. Used a voltmeter to measure from the end of removed + cable to the + post on the battery. Got 12.6V. Proceeded to pull every fuse from the fuseblock one at a time (and not replacing). Also all the connectors from various aftermarket stuff until nothing but flasher relay is still on fuseblock. Pulled all inline fuses as well. Still 12.6V from +post to cable. Read that it might be alternator so pulled both the 2 wire connector as well as the heavy red wire. Still 12.6V.

Trying to get armed with some suggestions for tomorrow. What's left to check? Pretty much anything with constant power (key off) that might be grounding out? Starter maybe? Thanks in advance for any suggestions.