1983 3.8 GM V6 help needed from someone that knows these engines.

I typically go to work around 5 lol

 

Knowing that it is impossible to say that what you did to remove relocate and reinstall the distributor was accurate in its placement, or for that matter what you have done to insure accurate timing relative to TDC, your guess would be better than mine for sure.
At this point of loose pushrods, I'd be inclined to start over with possibly doing an increased tear down to confirm proper cam gear alignment, valve train adjustment and if necessary, that all is good. You know the story, but I can attest that some tell stories.
Regarding a lifter pre-lubing, if I'm correct in my understanding, and tendence not to overthink things, it isn't necessary because the oil acts more as a shock damping absorber and the adjustment should be just snug to spin the pushrod when properly set up with the valves closed.

This lifter picture was from a 350 V8...well worn and very tired. Only you know what you're working with and the work you're doing, all the rest of us can do is guess. I'm sure you'll figure it out. Good luck.

 

https://www.novak-adapt.com/knowledge/engines/buick-90-v6.html

I’ve been away from V6 Buicks for awhile, remembered something about the 77’s but this confirmed what I thought I remembered, there were both odd and even fire in 77. Shared crank journals, odd fire, single rod per journal, even fire.

This much I remembered, All the carbureted V6’s had an oil pump that was distributor driven. The first year for a crank driven was ‘84 with the Regal 231 SFI (sequential fuel injection) without distributors. The distributorless engines used a gerotor pump that was crank driven, “mostly” the transverse FWD cars with exception of the 1985 Oldsmobiles 98’s,,they used a distributor that year only but by 86 were all distributorless.

And FWIW a quick and dirty trick to ****yze the GM carbureted cars with the computer. We would (unapproved by GM) disconnect the four wire connector from the distributor to the ECM in case of a poor running engine or a no start condition and try to start it. If it would start it would run and idle, you could rev it up but remember no ignition advance so it would run but not optimally. That could,help you in figuring out if the computer system or one of the basic systems in the car, low voltage, primary or secondary ignition, carburetor was the at fault area.