Wheels: 2000 Cobra Rs?

I ran into a pretty good deal for original 2000 Cobra Rs (18x9.5)... got two questions before I make the (necessary) plunge:

1. Anyone have streetable problems with 275/35-18 tires (front and rear) installed on stock susp? Im in the tune to lower the car later too, but dont want to pass up a good deal on wheels now.

2. Ive heard that 18x9.5 Cobra Rs have more of an offset and can "stick out" from the front fender wells. Is this true? How noticable? Pics?

I know the Cobra Rs have been done A LOT lately ... but have been after this wheel for awhile now, always been a favorite on that car.

Okay 32V thanks... first i want to make sure we're comparing apples to apples though, then i think i have some math to do

The stock 99 cobra wheels i have installed now are 17x8 with 30mm offset and 5.72 backspace...
and the 00 Cobra R's that im looking at are 18x9.5 with 20mm offset and 6.12 backspace...

How again can you tell if the width from the mounting surface to the outside lip increases, making the rim "stick out?"

PS Still havent gotten a response to installing 275/35R18 rubbers with the rims, anyone run into problems with this size?

I figured 275/35R18 only because the total diameter and circumference was closest to the stock tire size... things like speedometer, rear end ratio, and those types of things wouldnt be affected, well not by very much. Heres the link: Tire Dimension Calculator.

I found them at tirerack.com, looked like all major brands made them too not just the no name house brand.

The rims that I found were/are original Ford 2000 Cobra R... I had a lot of trouble finding the actual specs (offset/backspace) for the rim until I went to Ford Racing's website. Here's the links to those too:
Stock 99 Cobra
2000 Cobra R

With these specs it looks to me like they Cobra Rs might stick out, close to an inch further than the stocks. But im pretty sure that im doing my math wrong? Basically converting everything to MMs (including backspace and rim width) and seeing what the distance is from the hub mounting surface to the outer lip, thats all that I care about. Is there a formula or something that I can plug numbers into or should I wipe the dust off of the drafting board?