I used the JC core and it worked out really well. Sometimes it just costs a lot of money to get over the hump! What I did find remarkable was how quickly it warms the cab up.
If you are into an at home repair, you can pressurize it with couple of pieces of heater hose and some valve stems clamped in the ends. Use a bicycle pump to add a couple of pounds and then immerse it in water. After finding the leak, pull the fins or webbing off around the leak. This leaves a nice salmon colored clean copper exposed. Do the repair and retest. I did this and it worked until it got warm and then it leaked again.
