1989150 5spd hung in reverse. before it hung every gear worked fine

If your linkage is jammed also then that's the problem but if you can freely move it to another position and your clutch is working properly disconnect the linkage and manually try to move the pawl with the wheels blocked emergency brake on engine off if it's stuck you might have been rolling foward when you put it in reverse and this jammed the reverse you can try to do it by taking out the drive shaft have someone depress the clutch and try to turn the output shaft with a pipe wrench wrapping the out put shaft with rubber so you don't damage the splines on it tighten the pipe wrench as much as you can with vise grips to get the rubber to grip the splines the pipe wrench and a long piece of pipe will give you the leverage you need to try to free up the sincros if it's possible are you sure your clutch is working properly and is the linkage jammed to check as stated before first but this is an old truck 30-31 years by door sticker date and if you were rolling fowarded when you put it in reverse you might have snapped the sincros inside