According to the guy I bought this from, the speedo was calibrated for a 3.42 rear and a 200-4R trans....for a typical GN. So I'm hoping now that the speedo will still read right and the odometer will work also.
The trans gearing itself has nothing to do with the speedo reading. It is/was based on a 3.42 rear gear with 26" tires. If you have taller or shorter (measured, not sidewall math) then the speedo/odometer will be off by the % difference in gear and tire height. 10 % taller tire and the speedo odometer is off 10%. If you want to get the correct driven and drive gear combo you can go on one of the many calculators on the internet or calculate how many tire revs per mile and work backward to get the speedo ratio needed.