If you are refering to the old gearbox from MB minivans with 1st. gear=6.17 and 5th.=1 ? -then you dont need 6.17 final ratios to run 32" tires.
Your roadspeed will be terrible low with that setup.
By using that granny gearbox and stock 4.88 diff you get far better crawl ratio than using 6.17 final ratio and the more common 4 and 5 speed gearboxes.