wheels

Hey, havent posted in a while. I'm going to replace the stock rims on my 240sx and am not planning to do a 5 lug conversion. I just got the parts for my rb25 and with my neighbor am planning to start soon. I'm looking more towards speed performance aspects than drifting. The bodykit I'm getting is on order from japan, and a version of it can be seen at http://www.importfan.com/product.asp?0=0&1=0&3=4278

My question is, for best performance should I go with 17x7.5 18x8 or 18x7.5 on the wheels..also what offset would be reccomended for a widebody which would lip over the wheels as in the picture?

if its gonna be street driven but used for drag I'd go with 17-8 in front and 17-9 in back, offset should stay the same I think, cuz the wheels will be wider and stick otu and the body kit should stick out enough to go over them