I may be wrong, but I believe you have to remove the pin to put in new springs. A 50 year old truck probably needs new pins anyway, mine certainly did. I find the best way is to drill the old pins out with a drill press. If you use a letter "R" drill bit, you will have a perfect size hole for the replacement hinge pins. Be sure to use a drill press to get the hole straight, then reassemble with the new springs, and pound in the new pins, they will stick out the other side, just grind that end off.
