im running ams rear over fenders and 30mm wider front fenders. Wondering what offsets would be the closest to flush any help would be nice!

I need a wide tire in the rear because of the power it will be makeing.

Id like to fit a 325 or wider tire in the rear on a 18 inch rim.

the front a 225-255 would be fine

 

A 325 or wider?? Why do you need such a wide tire? You will want probably at least an 11-11.5" wheel for such a thing.

 

That would really be overkill on the width. It would not work well even if it fit. I would say take a look at the 315/30R18.
If I can help let me know.