Okay, before everyone laughs at me I am new to brakes and suspensions. I have a 69 camaro. It has front disc and rear drums. While I was doing some tranny work. My car was on a lift I noticed my rear brakes didn't work. I was giving a little gas and applying my brakes. The rear tires kept spinning. I don't know if this is normal. I noticed I only have a Master cylinder, splitter and booster. I didn't see a prop. valve. On a side note, when I drove my car on the street it stopped great and never pulled to the left or right.

Your rear brakes should work no matter what. Have you tried to adjust them?
As far as the proportioning valve, it should be there underneath the master cylinder. Trace your front to rear brake line. You might have an aftermarket dial type proportioning valve for the rear brakes.