Feel free to ask for yourselves, but when I inquired about these rotors earlier this year, I was told by MBM that they are
service replacements for an MBM conversion kit. I know it looks as if in the fitment menus that they fit as one piece K-H replacements, and you could assume they would, but I was told they don't.
The kit looks a lot like the standard reproduction slider-style spindle and bracket kit, and like Dr. Diff, uses sleeves to make the small upper ball joint fit. MBM says they use the '73-up repro spindle on all their conversion kits, and we know the early K-H hub and rotor assembly won't interchange with the '73-up rotor.
2627 SPINDLE SET - Mopar Spindle & Caliper Bracket Set
The kit is available with either 4" or 4.5" lug pattern rotors.
A Body Disc Brake Conversion Kits
These rotors might work with the '73-up factory setup, allowing you to run SBP wheels on the later brakes. I can't imagine why, but I suppose somebody might have a reason why they would want to.
Like I said, feel free to confirm, but please do before sending your money and getting into a situation where you need to make a return.