Thinking a little more on those lifters. Is there a possibility of them pumping up and lifting a valve or two off the seat at 5500. Reason being my 383 had the 509 with crane anti pump ups and I set them at zero lash. 4.88 gears 29,5 tire 117 mph, 11.65 you can figure the rpm out. Easily would have went faster with a high stall converter. (Had a Street Hemi vert)
Just looked at the Wallace calculater 6887 rpm. Never needed a tach, shifted by feel. It screamed they all thought I had a small block Chevy, were they supprised.