Depends what you're going to be doing with your FJ. Show, Mud, Sand, Highway, etc. As for size that's a matter of personal preference.
I run 29 X 10.50 Interco Thornbird TSL on stock rims on my 72.
TSL Thornbird | Interco Tire But I also live out in the country and cross rivers and streams along with lots and lots of mud and snow so I also don't have a lift. These tires are not highway tires (Loud and won't last) but look awesome if you live in town and just like the WOW factor.