I don't completely understand the post. Does the truck roll in neutral? Or are you still in gear with the clutch depressed? Is the parking brake cable adjusted and working? Roll back with the park brake is possible, roll forward will activate the "parking" brake(it is a leading shoe thing) if the park brake is not fully released. The effect of depressing the clutch, might be a bad throwout bearing..again I may have misread the post(my bad often). With the truck lifted, and free roll at each wheel, the shoes are not the issue. I would look at the parking brake adjustments. With a good light, and some contortion you can just see the shoes move when the parking brake is engaged and released. Let us know what you find.

Steve H