I may have misinterpreted the 1 1/8" BMC spec. Some mention of this being a dual bore diameter of 1 1/8 & 40mm. 40mm is like 1.57". Obviously there's no way this would bolt up if that's the case.

The 2 bolt flange design and pattern is some kind of fairly new standard for interchangeably.

Maybe some options...
Powerbrakeservice.net

Some corrections ...

Chevy K20/K30 Truck '77-'86 Metric 3/4 ton calipers
RAYBESTOS FRC4156, FRC4155 D370

These are not D52 pad format, but D370 which is slightly different. Rotor thickness specs for these calipers is the same as my D52s - 1.29" max & 1.21" min. The rotor diameter is 12.5" instead of the smaller D52 11.87".


I'm going to contact Dynatrack and see how they work their D44/D60 conversion. The D370 is normally a Dana60 caliper along with the D149 (3.38") format. What I want is the D44 6-5.5 pattern but with the D370 (3.15") calipers. Match that up with the RAYBESTOS MC390426 1 1/4" BMC if it'll bolt in. Definitely need a proportioning valve to cut down on the pressure to the back. Looks like it'll be about 2x what it should be.

Edward