2,500-2,800 should be good for a fresh full pressure 235 engine.
I held my 55 model 235 (recently rebuilt) in my 1 ton to 2,400-2,500 for about 8,000 miles in one month, seemed to do fine. It would go faster but burned more fuel and didn't seem as happy.

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-