I think a bed lift alone would look bad. Body lifts are generally not a good idea. Having said that, I did make a 3" cab lift for my truck to help clear my transmission. I used 2" X 3" tube with 1/4" wall. I'm pretty sure it will be as strong as if the cab were bolted where it was supposed to be.

•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-