'93 240SX: 225/40-18" on wheels with Toyota 5x100? Adapters?

[stratmatt777]

My mom just got a 2007 Toyota Corolla S with Motegi Racing 18" wheels with 225/40-18 tires on them. She does not like them at all so I am wondering if I can put them on my '93 240SX. A Toyota Corolla has a 5x100 bolt pattern and my research indicates that a '93 240SX has a 4 x 114.3(4.5") pattern.
Can I get these to fit by using some kind of adaptors and where would I get them?
What about offset or backspacing? Anyone have any experience with this?
(Sorry I got no results from my search of the site)

Using this site http://powerdog.com/tiresize.cgi and tirerack.com I have determined that these wheels must be 18x7.5" and that the 225/40s would make my speedo read 2 MPH low. I also don't know if 225s would even fit on a stock 240... Actually, 205/40-18s would be optimal for circumfrence making my speedo read 59MPH at 60MPH.
Assuming that these are in fact 18x7.5" wheels can they fit? Anyone know?
I have a hatchback if it makes any difference (probably doesn't).

Thanks so much! I have no other way of figuring this out!

[Crazyirish]

Its possible, but you would be spending a lot of money to put cheap wheels on your car. Sell the Motegis and buy something that fits without all that work.

[stratmatt777]

Its possible, but you would be spending a lot of money to put cheap wheels on your car. Sell the Motegis and buy something that fits without all that work.

Thanks for the reply! I will take that advice. 205/40-18 tires cost TWICE as much as 195/60-15 tires- so I cant afford to keep those cheap (and scratched) wheels anyway. Though it would be nice to have some 50 series tires someday...