Went camping on the weekend.
Us in our 4BD1T powered Rangie on 35'' tyres towing a trailer.
A good freind in his 94 3.9 V8 Disco auto also on 35'' tyres no trailer.
It was fairly even although we were not testing the fact, but the Isuzu had the edge up the hills.
The 3.9's dont like tyre mods etc. I would bet the manual would handle it better.
Justin

