some people have said they rub in the front w/ 245's, so 265's would definately have rubbing issues in front.
You could maybe get the backs to fit w/ the proper backspacing and beating/banging of the inner fender.
I would suggest you search on here and read some of the many posts about wide tires/wheels and decide if you're ready to use the torches, big hammers, etc to beat and bang on your car to get the wide tires to fit.
I wouldn't do it before some thorough research so you know what backspacing you need, etc for the look/fitment you desire.
Good Luck
By the way, a 50 lb. tire and wheel cost me $27 to ship USPS. 18's would probably weigh more an you'd prob. end up spending around $150 shipping for all 4
I'd have to agree with TheUser. I had a Camaro with 275/45-17's and while those were actually smaller diameter than my original 235/55-16's, I would think in your case that the 18's diameter and 265 width combined will cause rubbing in the front any time the car dips or when you turn your wheels enough. I had a friend with an '89 GT and he had no luck with his 245's on the front. I don't think the backs would be a problem, but that depends more on your suspension.