Outer Limits 4x4 Board

I have a 308 hilux 85 model and want to know if a diff 4.11 will be ok I have a 4.8 in it now i think it's was a 3y motor before so 4.11 will be ok

Depends on trye size and what you want out of it, purpose for fitting the V8, more speed /more grunt

As above, need more info

But as a vague guide, do as follows (assuming the car sees road use):
a 308 reaches peak torque around 2800rpm-3200rpm (repends on model, cam grind etc)
you want the engine to be on that revs in top gear at around 100km/h.

This system will give you good performance, it may not give you the best fuel economy. If you want that you may need higher diff ratios, and drive accordingly.

Example:
assuming peak torque at 3000rpm, G52 gearbox , and 30" tyres
you would want to keep your 4.8 in my opinion....
give you 3040rpm in 5th at 100km/h
2140rpm in 4th at 60km/h

My hilux with a 308 had 4.5 with 33 inch tyres. Seems to work pretty well. Would have like a bit lower on the freeway! But don't think you want to go to low. You should be able to pick a cheap centre and just change the back to see what it drives like in 2WD. Also side point it you changing diff gears or rebuilding diffs there is a change over month in 85 8th or 10th month (i think!) where the pinion bearings change size. (diffs the same excect bearings). A good bearing shop or 4x4 shop will know this.

I run 35" tires on the road with 4.88's, R151 5speed at 100kms I sit on 2350rpm.
The Surf loves this rev range and on LPG I get in the 17ltr per 100km.
Cheap and goes well

I ran 4.11s in mine with 33s and a 308 and they were a great ratio for a mixture of both road and offroad

I'm running 4.375s ,32" tyres an 308, sits around 2800 at 100ks