Heater Box Removal

I don't have an a/c . But, when I replaced my heater core in my 66, I didn't have to drain the radiator. Just disconnect the hoses going to the engine first, and then you can pull them through the firewall, if you disconnect the hoses directly behind the heatercore before u pull it out, chances are that it will spill fluid all over your carpet.

Depending on how much fluid is in ur radiator and system at the time, you will loose some fluid when you take the hoses off the engine, so be sure that you replace with fluid after, if hte drop is significant.