I would think there are plenty of "will this tire size fit" threads there to choose from.......do a search and start digging! 
Sounds like you are in the same boat as I am - looking to upgrade out of the 275/55/18s our Tundra's came from the dealer with.POLL - what tire size are you running (with out a lift)?
Have an 06 DC with TRD 18in rims running the stock 275/55/18 mich tires. Want to get a larger tire without having to install a lift kit, spacers, coil overs, etc...... What is the largest tire I can fit under a stock Tundra. Will a 275/65/18 BFG ATKO fit with no lift - don't mind taking the flaps off to fix minor rub. Do not really off road (except an occasional drive through the woods - nothing robust - 2 tracks a van could handle) so that's not a concern, just want a better truck tire.
What is the largest size tire you have tried (or can run on a stock tundra)
Thanks.