My 67 RS camaro has factory AC and I don't plan right now to purchase all the components to bring it back to stock. Is there an after market block off I can purchase for the firewall that would still give me heat and defrost in the car. Has anyone dealt with this before?

There should not be any reason to block off anything. The heater should work independent of the AC. Welcome aboard.

Here is what you need http://www.americangraffiti.biz/