I don't think is an issue with the swap. I have something similar on my NA and woks fine. I believe you have a pre-existing condition... thus the reason the old radiator gave up in the first place. (weakest link). I would start with the basics and work my way up.
clutch fan OK A/C fan kicking on thermostat/waterpump replaced ... also, hate to mention but a bad head gasket can build pressure in the coolant system and create cooling issues.