Back when I was unsure if my orginal Pattern 12 radiator was going to re-usable I started looking for a shop that could build a new one. I found an outfit down in Alabama US that makes big truck radiators, and has a side line making radiators for hot rods. If prices shown on their web site are correctly their prices are on par to buying a radiator for a modern truck.
They have a 38 Chev listed GM 2003 $395.00 38 CHEVROLET CORE SPECS: 17.125" X 25" X 2.25" INLET: 1.5" OUTLET: 1.75"
Here is their web address
http://www.cgj.com/ I have not bought anything from them so I can not say how good they are.
Cheers Phil