I don't think that's the spring spacer ya got there Tim. It should be the width of the spring, (2") for the 3600 not sure what yours will be I’m assuming you have 1 ¾” springs, and the length of the pad, which is 5". The dowel would be the proper length to locate it in the pad and go half way thru the spacer so the center bolt could still be picked up. You could get everything you need at any decent hardware store, no magic there. The object is to push the entire frame up not just the bed. Jack the bed up and it won’t be in line with the bumper. I doubt it we would have a problem Tim if that corner reinforcement were missing. After all, most of us aren’t bouncing our trucks thru fields or construction sites, which is what caused the corners to fatigue in the first place.
Jim, fabing a mount for your 54, 3600 would be a nice easy project. A bar of 1/2" round stock about 6feet long, a 4 foot length of 1.25"x 1.25"x 12 or 13ga. (3/32”) bent into an angle, (sheet metal shop). There have been a bunch of threads posted here on the ‘Bolt giving the dimensions.
Denny Graham
Sandwich, IL