QUOTE(mepstein @ Dec 24 2018, 05:14 PM)
See post #6
This is what I have found, all the bearings and spindles are the same. They are also the same as on many T1, T3 and T4 and 924.
The solid rotors are the same diameter but the T3 is 9.5mm thick and the T4 is 11mm thick. Early 914 is the T3 and later is the T4.
The 924 rotor uses the same bearings and is 13mm thick but has a diameter that is about 1/2in different.
The mounting bracket for the caliper compared to the rotor offset is different. When doing the 320 caliper modification the difference in the early and late 914 brake is found on the strut itself. The BMW caliper bolts right on the early but you must remove .125in of material off of the BMW caliper mounting surface to mount on the later strut, which gives you the difference between the two strut types.
There are several 4 piston calipers that are out there than can bolt up but will either need a spacer or machined face depending of the strut caliper combination.
There are as stated above several rotors available and some that will work but the overall diameter may need to be turned down.
There are also vented disc brakes for VW T1 that will go right on the spindle that should work with the 320 caliper for vented rotors and possibly Volvo, also wildwood and I am tracking down several others.
So it actually appears there are many options, if you have access to a machine shop. You can go vented and 4 puck calipers that will bolt on vented disc or bigger calipers on the solid disc.
It appears a machined surface later 914 caliper will work on an early strut with your solid late rotor with hub centric mount.
I am searching for more rotors and calipers that can bolt on with either spacing or machining for the caliper mounting face.