*************SOLVED*****************

Thank you everybody for the advice.

I decided to pull the Climate Control Unit out as in addition to no heat the AC was no longer working. It had worked perfect before I replaced the heater core. I thought that was kind of odd. When I pulled it out (hoping to see a loose connection) everything looked tight. I realized the long plug on the back of the climate control unit looked the same as the long plug that goes into the stereo. Guess what... it is the same exact size. I switched plugs and the heat and the AC work.

I had never put the stereo back in as since I had to take it out to fix the heater core, I thought it would be a good time to upgrade.

Anyways long story short, the radio and climate control plugs are the same size. remember which goes to which!

thanks