If you change the size of the front brakes or the size of the rear calipers it changes the proportioning. B110 brake proportioning is front small calipers with rear 11/16 cylinders.

As you know, changing the size of the master cylinder does not affect the proportioning at all.

With the 13/16s, I don't recall any report of problems with brake action (a lot of guys do this). Is it not working right? If the rear brakes lock up too soon, it is bad. What you can do is:

1. swap the rear brakes (which means swapping the brake backing plates, so new axle bearings are needed)

2. Put the 1200 rear axle assembly back in and only swap the pumpkin (center section) to the H150. It fits in the 1200 housing. You do not need a spacer, just use three gaskets and torque to specification.

3. Use an adjustable proportioning valve. Most guys get them from old Volvos.

PERHAPS the proportioning valve from a Datsun 210 will make it work acceptably. It was used with 13/16 rears and 12" or 13" fronts. So it should work on a 1200 with 13/16 rears.