One more cooling issue

I have a 72 duster 440 .030 over getting up to between 210 and 220. It has a dual core champion aluminum radiator with a 2950 CFM puller and an auxiliary pusher. 410 gears full spook rear end and 727 trans. There is no miss in the motor. No signs of a head gasket issue or crack in the block. No coolant in the oil or oil in the coolant. Checked for exhaust gas in the coolant. Zero. No leaks. 70/30 water/coolant mix. Temp remains constant idling or driving. Unless I’m going downhill with very little stress in the motor Laser temped the system. Inlet 178 outlet fluctuates between 178 and 163. I noticed that a couple of cores don’t seem to be flowing very well and one not at all. Would this account for the temp fluctuations at the outlet? I’m leaning towards the radiator being the biggest issue here but wanted to go to the experts to get some more input in case I’m missing something. Can you recore an aluminum radiator? Or is it even worth it?? Thanks in advance!!