Disregard the previous replies since they don't help much and kelly doesn't seem to follow what bushings you are talking about. I know the ones you speak of.
There are 2 bushings that go through the steering rack itself where the rack bolts to the K-member supporting the engine. Factory bushings are rubber and tend to flex a lot then dry-rot over a few years. There's a company called Energy Suspension that makes these bushings out of polyurethane. They are a lot stiffer and last longer than rubber.
Here's a link to your application.
From here on out if you need information on your Mustang don't ask here on Yahoo as these people know not what they speak of. Go to the site I list below. The Corral is one of the oldest, if not THE oldest Mustang website on the internet.