17 inch Mustang rims..
What is the width and backspace of the rims you have?
The 1.25" adapter in the back should put you where you need to be if you've got 5.72" backspace Mustang rims. But there's a few different backspaces for the stock Mustang wheels, so make sure you measure.
As far as the center register goes- the hole for that centercap is smaller on a mustang rim than it is on a Mopar rim. This means that the mustang rim will not sit flush against the hub on your brake rotor. The wheel will hit the outer edge of the hub before the rim is flush against the lug surface, so there will be a gap between the inner mounting surface of the rim and the base of the lug nuts. The caliper is not a problem.
You can use a hubcentric spacer to correct that issue, like these for example...
http://www.ebay.com/itm/2pc-FORD-MUSTANG-94-13-HUB-CENTRIC-Wheel-Spacer-1-4-Inch-/390574334346
Now, I haven't done business with that company, I just searched for a hubcentric spacer. You'd need to make sure that the center hole in the spacer is large enough to fit over the hub on the rotor ( I have no idea if those spacers will actually fit). Most won't, the center bore on the spacer needs to be ~71.2mm.
DO NOT USE WASHERS!!!
Here's a picture from the 17" cobra rims thread
This shows how the hub has been turned down on a lathe so that it fits the Mustang rim center register. Normally, the rotor would not have a stepped end on it, it would be straight all the way out the the edge.
What is the width and backspace of the rims you have?
The 1.25" adapter in the back should put you where you need to be if you've got 5.72" backspace Mustang rims. But there's a few different backspaces for the stock Mustang wheels, so make sure you measure.
As far as the center register goes- the hole for that centercap is smaller on a mustang rim than it is on a Mopar rim. This means that the mustang rim will not sit flush against the hub on your brake rotor. The wheel will hit the outer edge of the hub before the rim is flush against the lug surface, so there will be a gap between the inner mounting surface of the rim and the base of the lug nuts. The caliper is not a problem.
You can use a hubcentric spacer to correct that issue, like these for example...
http://www.ebay.com/itm/2pc-FORD-MUSTANG-94-13-HUB-CENTRIC-Wheel-Spacer-1-4-Inch-/390574334346
Now, I haven't done business with that company, I just searched for a hubcentric spacer. You'd need to make sure that the center hole in the spacer is large enough to fit over the hub on the rotor ( I have no idea if those spacers will actually fit). Most won't, the center bore on the spacer needs to be ~71.2mm.
DO NOT USE WASHERS!!!
Here's a picture from the 17" cobra rims thread
This shows how the hub has been turned down on a lathe so that it fits the Mustang rim center register. Normally, the rotor would not have a stepped end on it, it would be straight all the way out the the edge.