Your logic sounds right, although your truck may weigh less than 4200 empty. (my 52 1 ton weighs 4400)

You may never lift the entire trucks weight with the jack at one time, but best to plan for a bigger jack that you think you need any how.

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-