I've read about quite some issues at times with SSBC brakes from people who used them. Most seem to evolve around mismatched Mastercylinders and front/back-brake balance.
The most important items are the caliperbracket adapters.
But if you're handy enough you should be able to design/make them yourself.
These adapters fit much easier 'inside' the back of a 11.75" discrotor than a smaller 10.7 rotor. On a fullsize C-body, I personally wouldn't want anything smaller.
I made adapters like these for a few of my cars already. Even on the older Chryslers from '60, '62, '64 and a '73 Dart I'm running the same '73 rotors and calipers, mounted on the original drumbrake spindles by use of self-made adapters.
Here's the adapters for a '60 Chrysler;
And here for a '64 Chrysler;
A '66 Chrysler will have almost similar adapters as the '64 models, as can be seen by the pic on the SSBC-site.