The left rear wheel is squeaking while it is rolling. Not a constant squeal,
but an intermittent squeak, at about the same place in the wheels rotation.
I can hear it up to about 20 mph, but by then engine, road, and wind noise
drown it out. What could it be.

>>>that exact problem on my '64 Bus was a bad wheel bearing.  I didn't take care 
of it soon enough though and it froze.  Had to Dremel it off.