But your stock combination should easily be capable of 60. I used to cruise my 216 close to 60 on the highway at 2700-2800 rpm, 3 speed and 4.11, no problems at all, just noisy. A tach really helps put into perspective how wound up it sounds versus how wound up it actually is. That, or the gear ratio calculator.
I have had a T5 in it for several years and it's nice. Attached is a snapshot of my current highway cruising conditions. Stock 216 in a 50 half ton with a Task Force rear center section.
