Question about 4 wheel discs

I have a 65 Dart. I installed 73 and later front discs and Jeep Grand Cherokee rears. I am in the process of finish installing everything and I am running out of time for our big 1000 car cruise / show in my city this weekend.

My question is, can I use the stock drum brake master cylinder to get by for this weekend?

I bought a stock 4bolt disc/drum m/c and a Wilwood adjustable prop valve, but like I said, I'm running out of time. It will be all slow speed cruising with no highway driving. I'm mainly worried about safety not so much about what is technically correct for the application.
Will it work?

Any help is greatly appreciated.