285/70/17 is pretty standard and you might need to do the body mount chop with that also depending on the brand you get. You can do a search for body mount chop to find out more. I am going to be going with 295s this time around but with some modification you cang et 35s in there too.
really tire size comes down to a few different factors. If you're just wanting them for looks, MPG is going to be your main concern. If you plan on wheeling with them, size, tread style and weight all are concerns too.
35's look badass on the FJ, but cause the MPG to drop drastically if you keep everything else equal. Personally, I run 285's with stock gearing and get about 230 miles before the idiot light comes on. I have ARB bumpers from and rear and am running 285 70 17 Hankook MT03's. I'd love to go bigger but I'm not sure the MPG offset is worth it.
You can search the forums as this topic has been thoroughly hashed.