I wouldn't say that it's quite easy! just remember the bigger the tyres the harder it is for the engine to turn them!
With 31s you can just about get away with standard gearing but it is better to lower it with a 410 transfer box or better still a rocklobster or you fit a bigger engine.
Then to fit 33s you need to ideally lower the gearing even more and deffo have a bigger engine! To run 33s i've fitted a 1.6 8valve vit engine and gearbox, a modified vit transfer box with only the hi/lo gearset (not cheap!!!!) and a 410 transfer box, i also ideally need to fit sammy axles with vit ring and pinions to get standard gearing back. oh not to forget some major bulkhead modifications!
I would stick with 31s if i where you its easier and you won't break as much!
Also please stop shouting (turn caps lock off) Thanks matey
Oh and for a set of 4 of my tyres (tyres only) it's £330