The subject of tandem master cylinder plumbing is very complicated as shown in this article by a Studebaker guy:

http://www.studebaker-info.org/Tech/brakes/bf50014.html

And he doesn't even mention residual pressure valves, a subject on which "experts" totally contradict each other.

That's why I'm wondering if anyone has put a tandem master cylinder into a '36-'50 Huck system on a Chevy or GMC.

Ray