I have a 1966 K20, it was on the tree but the farmer i bought it off of put in a 4 speed on the floor. I believe its a muncie, but im not certain. I ordered a rebuild kit that covered multiple makes and models. I matched new parts with old when i reassembled. My question is, when I start the truck my drive shaft is spinning in neutral and when I have the clutch pushed in. (the whole truck is on blocks right now). I also cannot put it in 4th gear. What should be my best course of action?