I run 275/70R18 BFGs on my 2007 Yukon. I was running a RC spacer lift up front, but now use the Rancho Quik-Lift. I had to do trimming on the front mudflaps, and had to do the trimming on the supports for the front of the wheelwell liner (and then pull the liner forward). Everything just barely squeaks in. Mine run 10.8" wide and 33.2" tall by spec.
Your stated rating would be 34.1" tall and 10" wide. I don't think they'll fit without a LOT of work...I don't have that extra 1/2" of sidewall clearance, even with upgrades on mine.
That said, I'm loving the 275/70R18 for the same reason: tall and skinny is perfect in snow, rain, and mud that has a bottom to it.