14 bolt rear drum brake issuw

[My Alter Ego]

I'm looking for suggestions/answers to an issue I'm having with the rear drum brakes on my Corp. 14 bolt rear drum brakes. I "think" I know what the issue is , but want to put this out there for other possible suggestions that I haven't considered. The main issue is that the rear brakes will begin to increasingly tighten up after just a few miles and applying the brakes while "in town" driving. It eventually gets to the point that when I approach to stop at a light the brakes are already slowing the truck down before I've hit the brake pedal. When I put the clutch in or try to "bounce" off the clutch, the truck barely will roll by itself.
In my most recent outing I brought the truck home and immediately raised the rear and tried to spin the wheels forward by hand and it was as if the parking brake was applied, they wouldn't spin in a forward direction, but would spin relatively easily backwards. The ENTIRE brake system is new front to back (lines, master, booster, prop valve, calipers, pads, shoes, springs, drums, etc.).
What I believe to be the problem is the push rod between the booster and master is too long which would keep the line pressure up in the system, particularly the rear, disallowing the fluid to fully return to the master cyl.
Can any of you verify my belief before I start chasing possible solutions? Thanks in advance for your replies.