I used to shift mine a 6000 and go thru the traps at 6200. There was a guy around me that would shift at 8500. He would go thru 3 motors a year and was WAS WAY to dumb to figure it out let alone listen to me. He owned a machine shop (that explained a lot). Ran a '70 Bee all steel 3600#. Car went 10.20's back in the early '70's.