Bill...original fuel pump?

I don't know if the fuel pump is original, but I assume that it is. I bought the car with 114,000 miles (it has 179,000 now), and it has the stumbling problem when making right turns while 1/4 tank of fuel or less. I have a new OEM fuel pump and sock sitting in the garage, but don't want to go through the "fun" of dropping the tank and replacing the pump and sock until I have to...

I'd run it pretty dry (I did 1/2 gallon) and drop it out. Do it up and pick yourself up a set of straps first. You'll probably cut them.

maybe that'* the issue.

this is what I have always done to isolate wheel bearing noise:
Driving at those speeds, will the noise change if you put more of a sideload on the rear wheels? i.e. going around a corner. I noticed with every one of my wheel bearing failures (or uneven wear) that the humming whould increase or decrease, sometimes stopping, when I put a large enough sideload on the wheel.
Might also be worth it to check for hardened or worn control arm or strut bushings that could be transferring normal vibration through.