right now im at stock suspension with a 31x10.5x15... if i was to get a 6" suspension lift.. would 37x12.5x15 fit"? or 35x12.5x15? and what kinda stuff if i went from 31-35 would i have to do? like gears? spedometer? etc?

 

This may help http://fullsizebronco.com/forum/showthread.php?t=17022

Its a brother forum about broncos but its still about the same. From what i have read if you go with 37 and do any kinda of off roading you will end up brakeing axles and shafts or breaking the ttbs. Also you dont have to change the gears but if you want any power and it to go down the road like it did you need to swap the gears out and if you do any offroading need lockers