3/4T power brake question

[Ackattack]

I'm upgrading my 69 GMC 3/4T (aka No Buck) with a power brake booster.

So far I have the power brake booster and master cylinder from a 72 3/4T. (Along with the proper brackets, linkage, etc.

As of right now I am not changing to front disk brakes, so should I use the 72 power disk/drum proportiong valve or the 69 manual drum/drum prop valve? I'm thinking the drum/drum prop valve.

However, it seems the brake lines coming out of the MC are flipped. I can hook up the drum/drum prop valve pretty easily by flipping it upside down, but is this going to cause me any problems?

Thanks