[paul robert]

All big block engined hybrids like Bristols and Jensens overheat. No wonder, put a large cast iron motor in a confined space designed for looks rather than functionality and put in a radiator designed to just about handle things when the car is new and you should not be surprised to run into problems a few years down the road. All of these cars were not engineered to last (Bentleys were). look at them as fashion items for their well to do owners who'd exchange them after an average of 2 to 3 years.
The big myth about cooling is aluminium radiators. Been there done that. Aluminium rads do not cool better than their similarly sized steel friends.
They're just much more expensive. But.. they are lighter. makes sense for a racing or sports application but less so for a cruiser like a Bristol.
Simply get a large core modern steel radiator and spend part of the money saved by not getting a custom ally one on a set of high performance fans.Our cars were built when fan technology was in the stone age of fan technology.
Lastly, play around with your ignition timing. Originally Chrysler recommended something in the region of 5degrees initial advance. My Bristol runs at 13 initial and noticeably cooler than at say 10 degrees. Somehow each engine seems to be a bit different here. Since making these amendments I can sit in traffic for ages at 90 degrees. No sweat.