ok they said this "Sorry, I can not provide any of the measurements as they are proprietary"

kit comes with "Calipers,stainless lines, brackets, rotors, pads, and E-brake cables, and all mounting hardware"

Asked if it would fit MX13 F Series diff and got this

Unfortunately, the rear kit uses the factory backing plates. If you take some pics and measurements, it's possible our quad caliper bracket "might" work as it does come with backing plates. You'd have to pull the axle and measure up the pattern on the F series backing plate, where it bolts to the axle housing.

Im thinking if l get the kit for RA40 and run St141 backing plate it should work