Thanks for the replies.

I've gotten the old Proportioning Valve off and cleaned it up nicely and reinstalled it loosely. I need to run a new line from the front to the back still, it's in my next order of parts. I'll swap the 3/4" cylinders for 5/8" cylinders and go from there. I read through several different brake articles and the Rear Brake Bias article and it made some sense but this has cleared it up for the time being. 

Russ I'll add a servo down the road. For right now I'm just trying to get the car road worthy by July and then work on it as time/money permits. I want a running project and right now it's a bit from that but I'm creeping closer and closer to a running Mini as the days go on. 

Thanks again guys guys for the help. 

I've wondered this question myself.

My ole race car had an adjustable valve mounted close to hand brake/seat location. Would like to put a proporting valve back in.

Think for me the MS72 would fit the bill.  

If MS72 is what you go with, anti-seize the threads on adjuster .  

check the articles section and look at the articles on brakes.  One of them gives the rear cylinders to use with different set-ups.

As for the adjustable rear brake regulator Keith Calver did a "make your own" article in the August 2002 Mini Magazine.

If you installed the MS72, how would you test your brakes to adjust it?

If you are installing the Cooper S front disk brakes on with a single circuit system, using all the parts as installed on the Cooper S is the easiest.

The 21A1774 is the pressure regulator for the Cooper S.

The Cooper S had a power brake booster (servo) such as 21A1293 through MKII. The 13H7940 was used on MKIII Cooper S.

I do not use one on my MKII, but that is something to consider.

Russ

Clean and reinstall the proportioning valve now on the Mini...BUT...switch out the 3/4" rear wheel cylinders for 5/8"/0.625" with the 7.5" disc brakes up front or you will be swapping ends in the wet, dry/dusty road conditions under hard braking.

I'm fitting my '74 Mini 1000 (12" wheels) with ALL new brakes. My set up is of the Single Line variety.

I'm working from the rear of my car to the front and I'm at the Proportioning Valve.

On the rear I have replaced everything, there isn't a single old part left in the brake system or suspension system for that matter. I didn't spare any part or try to salvedge anything as I feel that this isn't an area to cut corners!

I'm running these

As I work my way towards the front I'm confused as to what Proportioning Valve to purchase.

This one:

Part No: 21A1774

Or:

Part No: MS72

The Front brakes will be converted to 7.5" S Discs.

This Kit or something extremly similar: Part No: C-AJJ4028MS

Thanks for any answers or advice on my brake system.