Yep, back when the trucks were new they might have all had the same shim.
Now 50 or 60 years later with sagging springs and perhaps some modifications you'd be smart to double check what the angles are and adjust if necessary, that's what really counts.

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-