I have that guage too. I have a 76k reading up to 150mph, a 78F reading up to 150mph, and another 78F, this one reading up to only 85 or 90mph. (ive had it up to at least 95, estimating my speed by the speed change per interval of 1000rpm. but that engine had the notorious dry camshaft problem, ending that road trip 160 miles in.)