While my truck has a 6.17 rear (with 7.50x20 rubber) so my experience might be a little different than that of a smaller truck with a higher rear ratio but smaller tires. You'll probably find that 1st in the 4 speed isn't useful except for creeping into tight spaces or maybe pacing a parade you've entered or if you're moving a heavy load in soft soil conditions. If you can handle shifting without the synchronizers the top gear is the same. The only thing you loose might be a little flexibility in some situations for maybe a little better ratio spread for unloaded cruising around town and slightly quicker shifts. I am also under the impression that the 4 speed box might be slightly stronger than the 3 speed from the same period.

1946 Chevy Pictures
1946 Chevrolet 2-ton. In family since new. Splash oiled 235, 4 speed main, 3 speed aux, single speed 6.17 rear. Original GM supplied 12' stake bed, paint on sideboards is still from the factory.
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