275/40/17's will work just fine on all 4 corners, rims would be 17x9's with 5" backspace with the Legends. That's exactly the same combo I run.
Tire is a little short, but not horrible. I've posted this a million times, but this is my Challenger with 275/40/17's all the way around on 17x9, 5" backspace Summit Legends.
In the front with the 275's I did need some additional camber to keep my tire from rubbing my passenger fender when going in and out of parking lot driveways and such with the wheels turned. I'm at -.9*'s and have no rubbing now. But I also sit pretty low, a little extra ride height and it wouldn't have been an issue. Also, I never had any issues with rubbing on the driver's side, so some cars may not need much of anything. I did remove the mid-fender braces on the backside of the fender, but again, my car sits pretty low. Only 3.5" to the header flanges.
I have a B body rear with Dr Diff 1" offset hangers and brackets, but I have a ton of space. The 17x9" with 5" backspace should work with the stock e body 8 3/4 and spring locations. It'll be tight, as that's about as big as you can go without offsets, but it should be fine.