The Ford Racing springs would be a great choice if you want to lower that specific amount. The specs for the Ford Racing springs are 1.2 inches front & rear. Steeda springs would be another great choice. They lower 1.2 inches in the front, but 1.5 in the rear. They lower more in the rear to even out the ride height and improve the looks.
The Steeda springs are on sale right now too, due to a holiday sale until 2009.
Here is a link to each option...
Ford Racing -
http://www.stangsuspension.com/store...idproduct=1573
Steeda -
http://www.stangsuspension.com/store...idproduct=1441
On your second question, I assume you may have been asking about alignment being off? When you lower your Mustang, you may have a bit of negative camber (tires leaning inward) which causes increased inner tire wear. There are two ways to fix this problem.
1. Camber Bolts - cheapest way to fix the problem.
2. Camber plates - best way to fix the problem.
You can browse around our Camber Plate section to check out the differences...
http://www.stangsuspension.com/store...?idCategory=29
Also watch this video
http://www.stangsuspension.com/store...?idproduct=970
Its a video we produced which shows some of the differences in alignment products.