98 Ranger with rear wheel brake having slight drag (1 wheel only)

Greetings: I have a ?98 Ranger with about 250K miles. Recently I serviced the rear brakes. The following parts are brand new: brake hardware (springs, etc), shoes, wheel cylinders, and drums.
Currently, there is an issue with a very slight pulsating ?drag? on the right rear wheel. Problem does not appear right away when starting the vehicle cold, but develops gradually after a few miles. Problem is not apparent on the left side.
I have done the following in an attempt to remedy:
1) Measured the radial runout on both drums. The left side read about 0.016?, and the right side (the pulsating side) measured about 0.030?. I don?t know what the runout specification is. I went ahead and got another replacement drum for the right side, with radial runout approximately equal to the left side.
2) I have visually verified, several times, that the brake adjuster screws on both sides are all the way ?in?, to allow max shoe to drum clearance. I have also verified that these are installed correctly.
3) I have verified that the short-sector shoe is on the front, and the long-sector is on the rear, on both sides.
4) I even tried shaving a bit of the brake lining off of the shoe, at the location which is dragging on the drum.
5) In an attempt to eliminate the parking brake as a possible cause, I have physically disconnected the parking brake linkage from both rear wheels.
Despite the above steps, the problem persists. Any ideas? Thanks