I'm 6' and while an AD cab is on the small side it's just fine, not to small at all for me.
I've driven about 8,000 miles in under a month with my 52 and never wished for a bigger cab, and that trip was with two people

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-