I wouldn't. The transmission was used in a truck smaller than 1/2 ton. The 261 is also a pretty reasonable engine. What is the first gear ratio, is it low enough to get a load started on a hill without frying the clutch?
I think the 4.10 gears will give you the speed you need and keeping the 4 speed is no question about strength.

Or because you have it and it is easy to install you could try it and see if it last?
Still probably best to first try the 4 speed and the 4.10, see if you even want overdrive.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-