I did a lot of research and had to learn a lot myself before getting my wheels, but it was worth the time and effort.
I ended up getting the Weld Sidewinders. I had it narrowed down to the Thrusters, Sidewinders and a couple of others, and the backspacing was the main reason I went with the Welds.
By the way, have you looked at the American Eagle wheels (
www.aewheels.com)? They have new designs (e.g., Series 102 and 194) that are exact (Or at least very close anyway) copies of the Welds at a much better price and they come in a 4.5" backspacing.
Unless I've missed something here on TS, you should have a clean fit with the 16x8s with a 4.5" backspacing if you run 265/75 or even the 275/70 sized tires. All of the members with the IS wheels, which are 16x8 with 4.5" backspacing, have had no reported problems with any kind of rubbing. And since Toyota sold the wheels (although with 265/70 rubber) as part of the IS package, I'm sure they verified the fit before putting them on the market. And the 265/75s are only about a 1/2" taller than the 265/70s so there is minimal difference between the two tire sizes.
As far as the center bore size question, I honestly don't know. Personally, I would contact a good wheel shop that sells Centerline or contact the guys at Centerline directly and ask if they'll fit. I've usually found that once a company learns that you're interested in buying their products, they're pretty good about helping out and getting you the answers you need.
Hope this helps and good luck.