I like #2 the best. I think 18s would look good all the way around, but go with an
18x10" rim on the back. This would allow you to go with a really mean, wide tire. You can also stagger the overall tire size from front to back and get a really cool look.

You could ask $1100 for your 20" rims/tires.

 

I think of the three, I'm liking the first option best.
Possibly doing the 18"s, staggered.
http://www.americanmuscle.com/machin...0509-stag.html

 

Good move if you go with 18s. To me, Mustangs don't always look right with skinny-sidewall rubber band tires. My rear tires are 295/45/18 and most people with 18s don't choose a tire that is as tall. I did because I like the look of a bigger tire on back--the classic muscle car/dragster look.

I think if you go with a 275/40 or 285/35 like alot of people here, you almost have to lower the car to make it look right out back.

On a side note, how are you liking the take-off muffler? I had my windows up/AC blasting when we passed the other day and I didn't hear it

 

It's not as loud as I'd like it to be lol,
I seem to have this obsession with exhaust now. Everywhere I go I'm looking and listening to other people's cars and their exhaust.

I'm probably just going to go with an american thunder axleback or something in the future.

Someone hit my car last night in a parking lot. I've got a wonderful dent on my rear panel, and some paint gone off my bumper. Yay!

 

That's too bad about the damage.... especially since you've only had the car for a short time.