Where you will be driving is also a factor..
The two times I have been to Florida I have yet to see any hills, unless they suddenly appeared you should be OK choosing an RPM on the low side of what folks recommend.

If you have a hard time deciding try to find some fellow Stove Bolters close to you who also have 1/2 ton AD trucks and 235's, and take a few test drives to see how different gear ratios feel.

Grigg

•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-