What is the 'runs great all day' RPM level for the original 216 and a early 60's 235? I'm looking for the comfortable cruising level and the maximum I can run--without excessive strain--on my '48 1 ton dually with a 8800 lb. GVW. I want to change out the final drive from the stock 5.14 to either the 4.57 from a 3/4 ton or a 4.10 from a later year. I'm trying to balance speed and load capacity using the original 4 speed transmission. Experience and advice appreciated!
