Same disk kit without the power booster.
1962-1972 MOPAR A Body Disc Brake Conversion Wheel Kit (wheel pattern 5x4) | eBay
Notice how it says you can use the same UCA's with the supplied adaptor kit? It uses ball joint sleeves to use the later spindles on the earlier small ball joint UCA's. So yes, you can use your original UCA's, but you will have a tapered adaptor in there to make it work.
I believe they're buying blank rotors and just drilling them for the 5x4" pattern. It's all 73+ parts with a small bolt pattern. They may also be machining the outer hub register down a bit, not sure. Or maybe that's why they say it doesn't work with all those 14" wheels, because the hub register is larger on the 73+ stuff than it was on the SBP brakes.
If it's all BBP stuff it will widen the front track width just like a BBP 73+ disk conversion. You'd want more backspacing than with a SBP set up. I was running 15x7" cop rims with 4.25" of backspace and 225/60/15's on my Duster before I went up to 18" rims, that would be about the limit as it was right on the fenders. You can run a little more backspace than that even on 15's, just depends on what you're trying to fit up front for tires. Are you staying with 15" rims?