Locked Rear Wheel help

[TwoFiftyShifter]

I finally got the brakes working on my jalopy. Just bled them, with brand new everything in the rear.... sorta. I used a drum off of a 72 K10 on my right rear, and the wheel is locked when i drive the truck on 1st gear - but not in reverse. Anyone know what could cause this? I even jacked the rear end up, and threw it into 1st gear hard, the left rear moves like it should but the right rear doesnt budge. The reason I seem to think the '72 drum is fine becuase the wheels act as they should in reverse. Do I just need to make more room in there? This is brand new shoes in the rear by the way.