Outer Limits 4x4 Board

I have a 75 series trayback and was thinking of fitting 35 inch tyres to it.
It has been lifted so clearance should be OK.
It is running a 2h motor and currently on 33's with standard diff ratio's. 4.1-1 going by the Gregorys manual.
I was thinking that the big wheels may be to much for the 2h to handle as it is a slug. It seems to be OK on the 33's just no great powerhouse.
I may need to change the diffs to lower ratio's if this can be done.
Any advice much appreciated.
Thanks Toyrox.

pu ton a turbo

keep ya 33's for on road and use 35's off road thats probley ya best bet or what he said turbo it. I have a mate with a 2h and done what u wanna do but he foud it is way to hard on the old donk on the hiway and now runs 33's on road and 35s off road hope i helped bud best of luck.