I think the widest we can put on our cars is an 11" rim. You definitely need to remove the quad shocks though. And don't even think about that wide in the front. 9" in the front is the widest.
10.5" is the widest I have ever seen the cobra r wheels. Amer. Racing makes the TTII's in 11" widths and that is the widest wheel I have seen for our cars. I run 17X10.5 wheels out back and I did NOT have to get rid of my quad shocks. Quad shocks help deter wheel hop.
I run 10.5's and have no issues with the quad shock. I think 11's would be pushing it, anything even slightly bigger I'd imagine would poke out further than the fender and wind up looking goofy.
I have 11 wide TTII's in the rear and just had to flip the quad. I also have a set of aftermarket LCA's and plan on removing it all together soon when I install them. no issues.