Like Scotty said don't forget the hub bore....most sites you have to dig to find it. It has to be the same 70.3 or bigger(like 73.1 or whatever).
You can use hub-centric rings to close the gap.
Nother wider than 9", nothing lower than 30+ offset and don't even bother looking for 5x115 wheels because they are all buttfcknugly.
Look for 5x114.3(same as 5x4.5) bolt patterns.
If you go on a site and it asks for your car type in some 94 and up Mustang GT.
Then come back here and see if you got it right.