I just took the lift rod apart that was on my nephew's model 73. The PO had really rigged up the top button, but it did work. Anyway, if I remember correctly drop the washer down over the internal rod then the spring will slide down over that. Then you can screw the release button. Use a leather glove or something over the button to keep from scratching it up as you use vice grips or pliers to screw the button down into position.
When you push the button down and you want the lift arm to float you will simply push the front lock button in while holding the button down then slowly let the release button slide up as you keep pressure on the front lock button. To release the lock button, simply press downwards on the release button and an internal spring will disengage the lock button. I hope this is as clear as mud for you.
