Most any aftermarket tachometer from the local auto parts store will do the job. I would suspect your engine is turning about 3500-3800 rpms at 50 mph, which is plenty. Part of that is due to the 4:56 gears in the rearend. But just remember, when those SUV people flip you off on their way buy, they are telling you....you are still number one!! You also need to remind them that your truck was here first and you could build a whole darn SUV out of the metal contained in just your front bumper !! If they get too fisty.... challange them to a 20 mph head-on. Then you will see who is laughing.....Randy grin grin grin grin