overheating

You probably have an "air bubble" in the cooling system. Here's a couple of suggestions:

1. Fill the radiator to the top without putting on the radiator cap. Start the engine and let it idle. If there is a bubble in the system, it should literally "burp" out as the engine gets warmer. Fill the expansion tank last. Make sure the radiator is topped off before you add coolant to the expansion tank. The bubble may also explain why part of the radiator is cool and other is hot.

2. Try finding a good Mopar radiator in the states. If not, get a good aftermarket radiator. The one you are using is probably not large enough to handle all that Chebby beatin' horsepower.