way to go bro.....my personal suggestion is to put atleast 225/55 R17 OR 235/50 R17 profile tyres on this fat a** american car.
thats the only way you'll get a muscle look out of this car
dont go with the fancy looking rims in the market these days......go for a proper muscle look...if you want to keep everything classic
and in original shape, the aftermarket 08 mustang rims are the best in the market
(in the picture below).
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220421121140QQssPageNameZMERC_VI_RCRX_Pr12_PcY_BIN_Stores_IT&refitem=360159465909&itemcount=12&refwidgetloc=active_view_item&usedrule1=CrossSell_LogicX&refwidgettype=cross_promot_widget&_trksid=p284.m184&_trkparms=algo%3DCRX%26its%3DS%252BI%252BSS%26itu%3DISS%252BUCI%252BSI%26otn%3D12
something like this, although this will cost about Rs 1,15,000 from US unless its available
in pakistan or something similar to this one.
IN THE END, obviously, it'll be ur decision and may be you have any other plans for your car,
but i just had a suggestion that i wanted to share.
cheers