I have a Mancini 3 core in my Savoy and it cools great since I got my coolant flowing good through it. I'm using a good older pump where the impeller is close to the housing so it's more efficient. The pulleys have a huge impact on the flow as well. I had aluminum race pulleys on it and then switched to some factory ones and presto now it runs cooler.

Are you running hot on the highway or idling around town? Just saying maybe it's not the radiator shruggy I tried everything else before I changed my radiator and found a system that works for my mild(maybe 570) combo. My engine gets up to around 200 when I cruise around on 90 degree days but that is really not overheating.

Gus beer

64 Plymouth Savoy
493 Indy EZ's by Nick at Compu-Flow
5-Speed Richmond faceplate Liberty box
Dana 60