Honestly, I don't think a "better" pad compound would overcome the fact that the caliper pistons are too small. I had the smallest bore master cylinder I could get (7/8") and it still wouldn't generate enough force over the given area of the pistons. In regards to break in, I made sure that I bedded the pads in correctly so there was definitely no glazing.
On top of the pistons being small, the rotors are also only 10.87" in diameter. If you combine those two less-than-ideal design parameters, the sum of the parts will not be sufficient for good braking. About the only application where I could see these brakes (factory K.H. type, NOT SSBC aluminum copies) being OK is on the early A cars because they are slightly smaller and lighter cars than the later models.
As we all know, Chrysler was notoriously cheap and it probably would have been cost prohibitive for them to re-design their A body brakes three years into the run. Would they have had to change the bolt pattern to 5 x 4 1/2" and/or go to 15" wheels to fit better brakes? Possibly? Were they going to do that if it cost them profit? Nope. They eventually did it in 1973 so they knew there was a need.
Bottom line though, SSBC did not do a great job engineering their product. I get that they were trying to satisfy a niche market and again, the idea was on the right track but the end product was not very good. It's hard to make an already marginal braking system better when you reduce the size of the caliper pistons!
The calipers are only one part of the system though. For those that don't know, to use these SSBC pieces, you'd either want to have a car already equipped with the early Kelsey Hayes cast iron disc system where they would be a straight swap or you would have to piece it all together to make it work - spindles, hubs, bearings, ball joints, correct bolts etc. Finding '65-'72 disc brake parts in good, usable condition is no small feat in 2023 either, especially the specific disc brake hubs. Most of it is worn out junk now anyway.
I regrettably went that way when I changed my Duster to discs however many years ago because it was lighter than the later '73 -up caliper conversion. Additionally, the early brakes don't offset the wheels outwards like the '73-up disc conversion does - I can't stand that. I even went so far as to source the impossible-to-find correct length, shouldered caliper to spindle bolts from a place in Australia. It cost more to ship them up here than the bolts themselves.
It was all a waste in the end because the brakes sucked.
