Go big ones hop it helps tonytoyota
I'm with Tony on this one! I have 33" 's on mine at the moment, admittedly they are a bit too wide. But when you buy your wheel set thats the set you have to run on.
As you said Seamus, you intend to lift your truck... It would be a shame to buy a smaller tyre and then regret it after. Which begs the question "What do you mostly intend to use the truck for?" If you want to do only road work with it, I'd fit a set of the original "Pizza Cutter" wheels on it! Lol
If you buy a suspension lift kit you have the space to fit the bigger tyre, but you may find that when on full articulation your tyres will be in your inner wing. I had seen this happen with one of my Dutch 60 mates. Plenty of height but the tyre grazes the top of the arch. I suggested to him to lower his bump stops to stop this.
With the bigger tyre, instead of regearing. You could fit a turbo kit which would help cut through the higher gearing. Or as Andy advised me to use the automatic gearing with the 3.7 ratio..
To allow me to fit my 33's I have a 65mm body lift which means when the axle meets the bumpstop on full articulation there is still 40mm ish space between the tyre and the top of the wheel arch. Like this:-
Had a bit of an incident! But thatsanother story!

But an experience that shows the dangers of offroading!
Hope the info helps..