Long story short - I've bought a Y61 patrol from a dealership, found out only after I got it home that it's had an engine conversion from an RD28 to a Y60 TD42. It's been turbo'd and mod plated.
It was doing 4000rpm @ 100kph so the rear diff was changed from 4.6 ratio t a 4.1 and now it's doing 3800rpm @ 100kph
I still think that it's way too high, it sounds terrible. I do a lot of highway driving and live out west so I need to get this sorted asap.

It's a 5 speed manual, the clutch isn't slipping and it currently has 31s

If anyone has any idea what's going on please let me know, I'm at an absolute loss as what to look at now.