Those look like standard '73+ sliding calipers which were used on both the 10 7/8" disc and 11 3/4" disc (don't quote me on those 2 exact sizes, I might be a little off).
So the kit you linked just uses standard '73+ LBP disc brake parts, but gives you a SBP rotor. That's a great idea imo if you need to keep SBP.
Those sliding calipers were used for a long time, so they'll be around and are inexpensive. I've experienced fantastic performance with them on any car I've installed them on.
