18" GT4 Wheels/Falken Tires
 

So someone locally is selling 18" GT4 Wheels with winter Falken tires (265/35R18) for $1000. i will look at the thread on the tires tomorrow. But my question is, would there be any problem putting these Mustang Wheels on my Z? The lug pattern size is the same as a Z 5X114.3. Thanks for the input and help!

Lots of potential issues but it probably will work. First off there are lots of years of Mustangs so that doesn't tell much besides the 5x4.5" lugs are probably the same as our 5x114.3mm lugs. However that is only one part of the equation.

The center bore on Mustangs vary between years and also vary front to back in some cases. On aftermarket wheels the center bore are usually pretty big and then different sized rings are used to make the center bore specific to different cars. I don't know if what you are calling the GT4 wheels have specific center bore to certain years Mustangs.

The next potential issue is the offset, which is how far out from the hub the wheels sit. Since this sounds like a square setup (all four tires and wheels are the same size) you would likely need to use spacers in the rear to get it to look good.

Another issue could be that the spoke design of the wheels may not clear your brakes however on the non-sport brakes that isn't usually an issue.

If you get us the offset and center bore we can probably tell you if they will fit.

Thank you for the information. I was looking online and the center bore sizes for the Mustang are from 64.1 and 70.3 (370z 66.1) and offset 22 and 45 (370z 47). I was also reading that the bore size difference can be "fixed" with some ring but I don't know if it would be too much hassle to deal with this now.