want tall sidewalls, will these fit?

[Ev and the boys]

Trying to decide on wheel and tire sizes before I spend all of my money. I have decided I really like a little bit of sidewall.

I see a lot of trucks with 18" wheels using 255/55/18 front, 275/55/18 rears, which I think gives overall of just about 30" rear, w just under 6" sidewalls. I have seen pics of a trucks with 6.5" sidewalls with 15s and 17s, and I really love the look. Unfortunately, the wheels I'm looking at aren't available in 17".

Does anyone have 275/60/18 rears? 31" overall?

Also, the wheels are avail 18x7 with 4.5bs, x8 with 4.75bs, or 9 with 5.25bs, so I'm kind of perplexed by these as well.