When I drove my 1 ton around the country, drivetrain near stock but with a 1955 235, 4.56 gears (you have about 5.14) and my tires were about 33" tall.
Running the engine at 2,400 rpm was about 52 mph, and I got about 12 miles to the gallon. Running any faster and the mileage dropped fast.

The truck weighes 4,400 lb empty, probably about 5,400 during the trip.

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-