the quadrunner has an odd bolt pattern 4x144 which I wasn't able to find any aftermarket rims for. way it get around it is bolt pattern adapters/spacers to get you to a more common 4x110. other issue for bigger tires would be getting some lift to get clearance from the fenders. I wasn't able to find any companies making any lift kits for the quadrunner 250's. based on the gearing of the differentials you need to keep a 2 or 3 inch of tire diameter between the front and rear wheels.
You can up the tire size if you want, but i wouldn't go much bigger then a inch if you do so. Only reason i say this is because the bigger tire you go with the more power it takes to turn them. So you can up your tires one inch and it shouldn't effect much in the way of your performance. Example: If you have say a 25x10-12 Rear and a 24x8-11 Front tire, then you should always keep the offset tire size. Example: Say you want to go bigger let's say by one inch, well you would then put a 26x10-12 Rear and a 25x8-11 Front tire. You can also change the width of the tire as well, just take into consideration interference in the steering system or rubbing if you do so. And welcome to the forum.
The Quadrunners have a 22" up front, I've looked at mine and thought that I could put a bigger tire on the front but if I do then the backs also have to go up to keep the front/back ratio the same unless I swap in a diff on a KQ. If you don't keep the ratio the same then it puts added strain on your drive parts.