You'll have to do some detective work to find a hose that fits. Mopar radiators were usually 26 inches but perhaps some trucks had something that was 31 inches. Do some radiator core research to find something that wide. If you can't find a Mopar that wide then you'll have to find another brand that used a wide radiator and a central mounted vertical water outlet. Not all engines used a central water outlet and some engines used a front facing or 45 degree angle outlet so you have to know what you're looking for.

My last build was a Duster with a big block. I put a C body radiator in the Duster so I had to search for a big block application with the C body radiator. Fortunately that wasn't too hard to find. You could use the same BB/C body upper hose and then lengthen it as needed with a metal tube.