cutlass overheating
 

I have a 83 4door cutlass... 350 motor and transmission. I've recently had the transmission rebuilt,complete tune up with everything from plug wires,plugs,distributor cap and rotor,fuel filter,I had the valve cover gaskets done,exhaust gaskets done, new heavy duty cooling radiator,new water pump,replaced some hoses,new radiator cap,new thermostat. At one time my car never overheated, but it started happening often so that's why I had things dealing with the water and cooling changed. For some reason when I run my a/c it will run hot. Like after I turn my engine off u can hear it like hiss and bubble and my overflow container will be filled past the hot line.... Also when its really hot outside like today I had my Windows down no a/c on but it was really hot outside. I made it home cut the engine off and it sputtered so I raised up the hood and that overflow bottle was to the top past the hot line again. Sometimes it does this sometimes it doesn't. It hasn't been doing it as much since I changed these things but I'm wondering what else could be wrong to make this happen? Any ideas? getting so frustrated I'm about ready to sell it but I love my old school car. Helppp....Also when the new radiator was installed we put the Orange looking coolant back into the radiator. Well when it overheated I noticed the coolant in the overflow container was still Orange but the color in the radiator was green. What's up with that?