Having just gone through this with my 65 4/4, I certainly feel your pain. Some thoughts to consider:
Your current radiator may, or may not be salvageable. Any good radiator shop in your area should be able to give you a prognosis. In my case, for instance, there were many small cracks in both tanks. Re-coring was just not feasible.
I was told of a radiator shop in San Francisco that could make very close duplicates of these radiators in brass/copper and would even reapply the original maker's plate to the top tank. But they only deal locally, and I'm on the other coast.
So I chose a new aluminum radiator from Ron Davis Racing in Arizona. The salesman there, Bill Williamson, is very knowledgeable about Morgans, and the firm as a good reputation. After painting the unit black, the only real difference you can notice is the shape of the top tank. RDR can even duplicate that, but it adds $500 to the price. Since the cowl covers the top of the tank, the difference is not really noticeable after installation.
The product was delivered ahead of the time promised and the workmanship is excellent.
I also know people who are also very happy with Griffin Radiators in South Carolina.
