My brother missed a 3-4 shift in my firebird with 1800 miles on it, and dropped it into second at about 120 mph. The tach zipped up to a bit over 7k before he got the clutch back in, not sure how high it really went since the tach probably had a bit of lag in it. The motor ran fine (including a few autox racing seasons) for another 110,000ish miles before I sold it. Those early F-body LS-1 motors were built pretty well since they'd gotten the major flaws out of them already with a few years putting them in vettes already.