Hi.  Does anyone know what a good rear gear ratio is for mission?   Ive got a gt1 stock car.  Ford 9",   7500 rpm
With  a set of 27" and 27.5" tires.   4speed trans.   I calculated about a 5.40 which is a guess as Not sure what the max km/h is.  And anyone have sets of Gears for sale?

Thanks!