My guess is 2,500 rpm tops if you want it to last.
But that's judging from my '55 235 and from other 235's that run a little faster with no problems. I haven't driven far in a 216 truck to have a good answer for you.

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-