correct bore diameter for manual brake master cylinder disc/drum

[gmhardwick66]

I have a 1968 chevy c10 that already has been upgraded to disc up front and factory drum in rear. It also has power booster in use now. I want to convert it back to manual master cylinder only. Will be installing your D52 front calipers. I am assuming the brake linkage is still the factory set up. I need to know which master cylinder/proportioning valve to go with. I have looked at your Aluminum Tandem M/C Kit with Bracket and Valve kits. BUT I do not know what bore size to go with. Like I mentioned I will be using factory drum in rear and your D52 calipers up front. Has anyone already done this and what m/c bore worked the best. thanks