Will these wheels fit?
 

They are 17x7.5 with a 40 offset all around, front tires are 255,45,17 and rear is 285,40,17

Mille Miglia ruims.

Both those tire sizes are way to wide for a 7.5" wide wheel.... the tires will fit under the wheel well, but I wouldn't advise running a 285 on that narrow of wheel.. A 285 needs at least a 9"-10" and the 255 needs a least an 8", pref.-8.5"

Isn't 7.5" a bit narrow for an FD considering they come with 8" stock?

if this is for a FD you are way off the stock FD wheels are 16x8 you will need to maintain that level or go higher. most people run a 17x8 or 17x8.5 and a 19x9.5 or 17x10. you need to reconcider your selection.

I was going to ask why you would want to run a narrower wheel than an FD wheel? FD wheels are really great wheels... Stick with those wheels and stick some 245's on them....