not sure where this should go but umm my 88 firebird had a 145 mph gauge in it and a 8000rpm tach and i switched it to a 140mph gauge and a 6000rpm tach cause they didnt have 145 and 8000 but anyways i want the tach and speedo to be right so where could i go or what can i do to get them recalibrated?

 

Not sure about the tach, but the speedo can be changed by changing the speedo gears. They are located toward the rear of your transmission. Its not that hard to do but you need to know which gears to use. Do a search on the board for it and there should be a site that calculates for it. It all depends on tire size and gear ratio.