Thanks for the feedback, fellas. I too suspect something is out of spec somewhere but don't know what. I suppose I could start swapping parts with known good guns and figger it out, but if it works as it is now, no big deal, I guess.
I think most of my problems were caused by the finish on the EA lower. It appears to be some kind of flat gray paint (pretty durable, though), not anodizing. For example, I had to clean up the selector hole on the right side and remove most of the finish in there because the selector wouldn't move freely. I put it in the hole and cowboyed it around until the wear marks showed me where the interference was. A few minutes with a rattail file and it was moving freely.
The bolt catch is also not moving freely, I suspect for the same reason. No big deal if I'm running it with a .22 conversion because those don't activate it anyway, but if I ever decide to shoot much centerfire out of this lower, I'll have to take that back out and polish out the interference.
I hate roll pins.
The trigger guard gave me a bit of trouble, too. The pins definitely didn't line up on that. Had to do a bit of filing to get it in. When the rear pin was installed, the guard was notably offset to the right by several degrees--enough to keep the guard from locking properly. I don't know if the holes in the receiver or in the guard itself were out of square. Again, not a huge deal. I made it work.
I've built a number of 1911s on aftermarket frames and there is ALWAYS tweaking of one sort or another to be done on those. Just wondered if it was supposed to be the same on ARs. BTW, I built four or five guns on Essex frames and never had any problems with the hammer or sear holes that so many have complained about, so maybe with this AR I was "due." But if it works, I'm happy.