If you wheel, I definitely wouldn't put it out before the rear tire.
I used to have just a 90 after my cat,
but I got sick of the noise and exhaust fumes so I threw a muffler on there and ran it out the back. Used a stock tail pipe and only had to modify it to go above the rear leaf spring. If you don't have a lot of lift, this probably isn't the way to go, but for 5-6" of lift, it's perfect. It is almost impossible (almost) for me to smack the tail pipe while wheeling. I didn't have enough room between the skid and the leaf spring to run the pipe, so this was the easiest/cheapest/KISS solution. This pic doesn't show it all that well...but you get the picture.