As the title says, I got to wondering- my '97 Mustang came with 245-45-16 size tires, instead of the 50 or 55 series tires it was supposed to have. The speedo is off by about 10 mph...at 70, it reads about 80! With so many tire sizes out there for Cobras,, how do I get a Stewart Warner speedo (the brand I plan to go with on the build) or for that matter, any speedo calibrated? Also, if I use a used donor speedo- does the state of Ct get picky about indicated milage, or does that matter since I could simply buy a new SW one?I know that there are drive and driven speedo gears, but how to find out which combo??????