which master cylinder for my c10?

[Pont406]

I searched and found 2 brand of masters for 72 c10 truck Delco Moraine and Bendix.Here is where it gets a little treaky. My 69 c10 had powered drum brakes with bendix booster. Now it has a basiclly 72 set up with bendix booster. I had some small brake problems and nailed down to a wrong master cylinder. Before we take my new proportioning valve and gut rear section to run adjustble valve from summit i want to check here first.
I have a reman bendix booster with delco master cylinder. Are they interchange or not? I had gauges install on the rear and readings were low. Dont remember the numbers but my buddy wants me to double it with using summit adjusting proportioning valve but only for the rear. I want to try a correct master first. He says that they are all intechange. So, do I have a right master on it now? Thanks a lot.