I had a similar problem but mine was a poor engine build. However, before I trashed the engine I had Arts Radiator in New Jersey build me a totally aluminium radiator (no epoxy) even my old engine ran around 200 degrees. My new engine runs at 190 - 195 (190 degree thermostat). Even at long stop lights in 90 + degree weather my engine temp doesn't move 5 degrees. Cost was about $400.
Very happy with my cross flow radiator.
http://artsradiator.com
708-782-8944
email
arts@ptd.net