Well, My brother and I put a 230-6 cyl. in the `48 1-ton when he had it(16 years ago).It had the cast-iron bellhousing and We made some brackets shaped like a wedge to fit the flat area on the stock crossmember to the angled mount area on the cast-iron housing.The mounts are long gone or I would send them to you frown .
I think that the GMC radiator will work for an inch or more clearance at the front of the engine as the GMC radiators sit more foreward,not at an angle like the Chevy radiators.

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!