[RichardJ]

>>Just to add insult to injury, on the correct MC, does the front port feed the front brakes therefore would the front port be considered the Primary Port?<<

On a dual master cylinder, the rear piston and port is the Primary Port and primary brake system. Force applied from the brake rod is applied to the primary piston first, but that force is applied to the secondary piston equally.

Pressure at the Primary Port and the Secondary Port is always equal.

There is no standard answer to whether the Secondary Port is used for front or rear brakes. GM switched some of their brake systems front to back, year to year during the time they were switching from drum/drum to drum/disc and even disc/disc.

FWD brake systems, especially import, use diagonal brake systems where the secondary port is connected to the left front and the right rear brake. The primary port is then connected to the right front and left rear. Because they are a dual disc/drum system, they use dual, tandem proportioning valves. Even more fun with ABS