The Posies or Patrick's lowering springs are for the 1/2 ton (3100) truck. They will not fit in your 3/4 ton (3600) truck. The springs are of different length and width. If your interest is in "lowering" the truck you could remove a couple of leaves from the rear springs. It will also soften the ride and you will not have the load carrying capacity of the stock spring. I wouldn't remove any leaves from the front springs because you'll constantly be bottoming out. You could go to a spring shop and de-arch the front springs, so they'll retain the near stiffness of the stock spring. I don't think there are any "dropped" front axles available for the 3/4 ton truck.
