Am I missing something for a proper brake setup?

[Apogee]

Yes, you probably should be running a 10 psi residual pressure valve in your rear drum brake circuit now, however you won't need one if/when you convert to discs. Residual pressure valves are typically either built into the outlet ports of the MC or as stand alone inline units some some OE and aftermarket applications. Since you're running a C3 Corvette disc/disc master cylinder, it won't have any RPV, so it is theoreticaly more susceptible to "burping" air past the cup seals when the retraction springs collapse the wheel cylinders.

Tobin
KORE3