I have almost all my parts for my 1969 disc brake upgrade. My car has stock front disc.

Doing the C4 front and RH 93-97 Z/28 (essentially C4) rear calipers

Does anyone sell the 1969 front drum hubs already machined with longer studs?

I am trying to decide if I should go with a hydro booster with my stock MC or a new step up that would work with this upgrade? Suggestions on an MC? Who sells just a hydroboost set up? Should I also use and adj proportioning valve?

If you will drive the car hard, the C4 brakes are barely adequate. For normal street use, they are fine. I rode on a race track with a guy who took off stock discs and put on C4 brakes, they overheated faster than stock brakes.

A stock master cyl won't work with those calipers, you need a much smaller bore. 15/16" - 24mm, or smaller for power brake use. use an adj prop valve.