I looked for a better pic but this will have to do.
On the right you can see my 3"BL w/poly bushings. My poly is made by Energy Suspension, the BL is unkown as it was on my rig when I bought it back in '93.
But as you can see the BL 'pucks' are wider than the poly. You can also see I have a big washer in-between the poly & the puck.
I put the poly mounts in back in '94 and never had an issue with thoes mounts eversence.
Just do NOT over tighten the bolt, you do not want to squeeze poly, it won't flex if it's bound up. I used nylon lock nuts to keep the bolts from comming loose.
PS ~ after I bought my K5 in 93 and a friend told me about poly mounts, so I bought the kit and started in on the install...come to find out my K5 only had 5 of the 12 mounts secured to the frame
crazy!