Hey mate.
ive had a few rb30 skylines and there a pretty good thing but even in a 1400 odd kg body there not exactly a torque monster. ive had gqs with a 4.2 efi, a 5l vn motor, a mild 383 stroker and a pretty full house 383 and the difference between them all was amazing.
to be honest i dont think even the 5l has enough torque for the size of a patrol- especially if your gonna go bigger tires and a few accessories- mine had 35s and bars and came in at 2400kg.
When i went to the stroker, i actually found it didnt effect economy too much because it had such an easier time of getting around and all the engines got around the 20 to 23l/100 mark around town. i also ran gas injection to make them affordable and it made the same power as petrol and very similar economy to that'd be a good way to go too.
And on the power front the tb42e made low 70's kw atw and cant rem. the torque,
the 5l 109kw at like 4500 and under 400nm,
the first 383 171kw at 3800( stock manifold) and around 600nm
and the full house 383 made 235kw at 4900( come racing manifold) and 680nm at 2800 and over 600nm from 2000 till 4100 with a baby cam- great off road.
So for me from what ive felt and seen the more cubes the better!
Regards,
Craig