Rims/Tires/ Lowering

i dont believe youll have any problems with the 19s, but id go with 18s myself, maybe even 17s esp if your lookin for performance. I have 285s on the rear on mine and 265s on the front and it looks awesome, plus its lowered, if you want an idea of how thatd look heres my website: http://www.cardomain.com/id/mustangmatt685

I have 275/40/17's up front and 315/35/17's out back and I only rub on the front wheel well liner at full lock, and I used to rub on the rear quad shocks. I have Steeda Sport springs also.

The trick to not rubbing is getting the right offset and not going crazy with the tire width.

My personal opinion is not to go more than 18's, because anything in 19" + wide + low profile is going to be over $200/each easily.

If you're looking for ride quality, you're not looking for 19" rims... past 18", ride roughness increases exponentially.

Performance-wise, most 17x9" tires can already accomodate the widest tire you can fit up-front without rubbing (265-275 mms) and in the rear (315s). 17" wheels & tires = less rotating mass than 19" wheels = faster car. A lot of drag slicks mount on 15" wheels, which are much lighter.

The largest brake kit for Mustangs I've seen yet are four-piston Brembos which need an 18" rim to fit.

You might not be worried about cost, but at 19", the cost of tires becomes downright obscene (18"s are bad enough!)... especially since most tires that size have crappy treadwear life.