I have the same setup as you do in a 51 GMC. Like you it feels comfortable to run at about 50 mph with it.I installed a tach just to see where the rpm's were, at 60 mph the engine was running at 3000 rpm. Just a reference point.
51 GMC 100 with 59 chevy 261 under the hood. 3 on the floor with 3.42 gear.
