Just some advice from personal experience I am sharing.
We were on our way to the Branson Meet, waaaaaay out in Eastern Kansas where there was nothing but high way, and one of the guys in our group needed to pull over cause something didn't sound right and feel right. Right front caliper was grinding on his rim. As usual the top bolt fell out and hen he hit his brake the caliper pivoted on the bottom bolt, and the rim stopped the caliper form going any further as he was driving, and as he stopped. Chewed the caliper up pretty good, as well as his rim.
LUCKY, the bolt did not fall out all the way, it was bent, and barely holding on, so we were able to get it back in there on the side of the road to get him going again, and he later fixed it when we got to Branson. It would of really-really sucked if he had lost the bolt completely.
Food for thought....
Every caliper kit I redo and resell has this already done to it when it leaves my hands.
The only reason why I think people feel the need to do the shim/sleeve mod is so after they remove the calipers for what ever reason (demod?) they can still be used on a F-body car.
Brakes are pretty important...you kinda need them, epically the front ones...I don't think its worth the risk to use the shim/sleeve mod with these as it allows too much play in the caliper bracket, and the more you use your brakes, the more play it gets till one or both of the bolts loosen up and thats all she wrote. Even had one local use RED non-removable loctite and grade 8 bolts and hes a pretty strong guy and he torqued them down hard, and know what...short time later, one of his fell out and trashed his nicely powder coated caliper. But he caught it in time, so the damage was not too bad.
I think ZZP is just trying to make a buck and not really thinking this one through. But I'll let them open that can of worms, cause they will just tell the customers who loose a caliper bolt, "they must of not got them tight enough, sorry".
~F~