Outer Limits 4x4 Board

My mates Spookey is running 32 muddies and runs way too fast on rocks. He already has rock-hopper t-case in it, but wants to drop the diff ratio coz he can't even use 5th gear on the highway at 110 (it just dies and has to drop back to 4th).
Any suggestions.
We've toyed with the Hi-lux or Patrol diffs idea, but would like to keep the standard housing.
Tanks
Brendo

What year does he have? i am guessing a 1.3 model.

u can get in sierra
3.7 in WT sierra
3.9 in NT sierra
4.1 in maruti sierra - rare to find
4.6 in vitara need two front diffs
5.12 in vitara need two front diffs

there are some in between but unsure of them

You could also remove the current rockhoppers out of it and sell them on ebay, then buy some decent ratios like a series4

Is it a d/d? I ran s1 rockhopper with 4.6 vit diff gears and 32s and it reved heaps. I currently have s1 rockhopper 4.8 ( toy diffs ) and 33s, so pretty much the same overall gearing as before and you,d think I would have learnt my lesson it still revs to hard 4000rpm 90/95km/h.
I only went with vit diff gears as there were no other transfer gears available when I 1st built my zook. But if you do go this way give Suzi 4 Wreckers a call cheapest by far.
Nik

.....and 4.3's.