Good and bad wrenching day yesterday.
Used yet more rivet nuts, this time for the chassis ground next to the battery. Replaced a through-bolt I had installed for grounds. (Fan harness, and battery > chassis ground) Finalized battery cable routing. Used another rivet nut for the battery hold down, no more body clip/retainer. Had to re-tap the shitty side post extender I need for the Ramchargers fan, and power tap.. I may need to rethink that approach, or buy a better post extender.
Decided to install the new Highway Stars A/C lines, close up the A/C system, and put a vacuum on it. Removed the seal from the back of my new compressor, it still had a vacuum, that's a good thing.
Glen's lines include a small aluminum adapter/bushing that has to be used with the new-style A/C compressors. I read that, read up on it, says it's required, but not how or where to install it. Process of elimination brought me to the thought that it fit in the outer discharge port.
I went to see if it fit, so I could understand the item's use. I wasn't paying attention, and tried to put it in the suction port, and it quickly fell into the bowels of the R4 compressor. Yay.
Used my borescope, couldn't see the part.. Soooo time to take the compressor out. Lots of fun.
Long story short, after a lot of shaking, more borescope use, brass hammer taps, smacks, etc - the adapter is stuck in the compressor, there goes $250.00 down the tube, the ruined unit was a brand new ACDelco too. I could hear it rattling around once, but couldn't get it to where I could grab it.

Ordered a new compressor, another adapter, and a new high pressure switch from Highway Stars...
This is the item that fell in the compressor, and yes - I am indeed a dumbass.