yes the 275/70 should work with the stock set up. Despite my better judgment, I just purchased the A/T4W 285/70/18's. Was between this and the 295/70 defenders but assume there will be minor rubbing. I'm on Tundra BBS with 1.25" spacers.
yes. 1.25" and trimming most likely. Can read through this if you haven't already
https://forum.ih8mud.com/threads/295-70-18-is-a-tire-size-that-you-should-consider.1244282/