Tire size for 18x10 wheels

[bigsarge81]

I really like the way my OBS looks with 20" wheels, but for city streets, it's a bit rough. I'm thinking hard about dropping to an 18x8 and 18x10 set-up. With this drop, the tires obviously have to tuck under the wheel well. The fronts are easy to find: 245/50 is right at the stock running height. But the back tire size is not so obvious.
If anyone is running this set-up on a lowered truck, what tire size are you running? I want to keep the stock ride height, which is roughly 27.7 front and 28.7 back.
The truck as it currently sits, and the wheel that I'm cosidering, are pictured below.
Thanks in advance,
KM

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I know this is an old thread but i wanted to ask what your wheel and tire set up is in the picture.