Hi, going wider tires for a IRS is not that big of a problem. If you are willing to shorten the axel, then why not use wider fender? I will be running 10 rims by using wider fenders. If its just to get the tires under the fenders, use wider ones. These are 10 cookie cutter;
See they fit, with three inch wider Fiber glass fenders.
You can also shorten you trailing arm by 1" per side, and a 8 inch rim will fit within stock fenders. I did a set of trailing arm myself, but have not needed them yet.