Proportioning Valve

Kern Dog said
Like Wayne stated, stock 4 wheel drum cars use what is actually a distribution block that has no proportioning function to it.
4 wheel drum cars, as well as cars fitted with 4 wheel discs, need NO proportioning valve. The drum cars rely on wheel cylinder sizing to establish the brake proportioning bias. Same applies to the 4 wheel disc systems.
Front disc/rear drum cars DO need some manner of proportioning so that each end of the car gets the proper line pressure. Wheel cylinders require much less pressure from the master cylinder to energize. Disc brake calipers are much bigger and require more pressure and fluid volume to operate. The factory 4 wheel drum distribution block looks like this:

View attachment 1715836098

The proportioning valve looks like this:

View attachment 1715836099

I'm not trying to hijack the thread but here goes as this may be related to the OP's question: I had a front disc brake conversion done on my '68 Dart and the brakes seemed OK for a while, the guy who did the swap pulled my Distribution Block and plumbed in an aftermarket adjustable Proportioning Valve (which started leaking almost immediately). I recently bought a new Disc/Drum correct master cylinder so I can go back to the Dist Block setup and get my dummy switch working again. The new mechanic installed it for me and plumbed the old Dist Block back in (I'd love to see a plumbing diagram for the original Dist Block if anyone has one???). The swap went fine and the front seemed to work well but the rears just won't grab to lock up when idling in gear on the hoist? There seems to be a little sigh/hiss/wheeze from the brake master after it first is depressed. So that leads to 2 questions:
1) Is there some sort of plumbing issue with the Distribution Block and can I get a plumbing map to make sure we have the lines in correctly?
2) What is the correct Brake Booster for my application? Does Summit Racing have a part number for one which is correct for my vehicle (1968 Dodge Dart convertible had a 273 before the engine swap)? I'm in Canada so Summit.seems to be the only Mopar shop up here.

Hopefully my problem is parallel to the OP's and our problems overlap a little so the answers will help everyone!

Thanks in advance.