I think it depends on the weight of the truck and the relative size of the front axle beam.
Some trucks the axle looks small and fragile, so jack each side.
Some trucks have real beefy I-beam axles and don't look like they'd bend easy, so jacking in the middle seems safe. Though fully loaded may still opt to jack separately.

Use a little guesstimation and common sense.

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-