1968 Dart Brake and Booster issues?

AJ/FormS said

The car does not care what M/C is on it, and the P-valve is in no wise matched to it. The only only differences between these two styles is that the drum-drum unit has 10psi hold-back valve installed in BOTH ports whereas the Disc-drum has it only in the rear.
And the DB unit has a larger reservoir for the front brakes. That is all.
You can make any Mopar M/C work on your car, whether DB fronts or not

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I had been told by numerous folks that the larger reservoir on the Disc side of the MC would also be set up to push more fluid to the calipers whereas the smaller wheel cylinders would get less fluid and that the MC would basically be proportioning it at the source and so the D.Block would be adequate.

Have I been steered wrong? Most of the replies to the posts seem to suggest that one still needs a P.Valve in line to the rear to dial it in.

I'd like to rule out the Distribution block as the source of the problem before going on to tackling the quite possibly leaking Vacuum Brake Booster.