Well, it seems like you've already discovered the first problem with your plan to scavenge parts from other Ford models to upgrade your car......the suspension and steering systems that these cars used don't provide any easy or practical swaps. The basic engine and trans packages stayed virtually unchanged from 65 to 95, with only a few parts that are specific to certain arrangements (you have to watch timing covers and water pumps, and an engine balance change for a couple of examples.) The bottom line is it is pretty easy to put a 5.0 in any Mustang ever made. The same goes for the transmissions.
Suspension and steering (and to a lesser degree, brakes) are a different matter. You are limited to the basic concept of a stock rebuild, a slightly modified stock rebuild (Shelby drop, better bushings, traction bars and the like) or you have to go full out to the aftermarket support. There are some excellent companies out there, and to be honest, the stock Ford pieces were not the most durable in the world. I used to drive my Mustangs daily, and upper control arm bushings and balljoints were frequent problems.
The easiest thing to do is a complete swap to stock V8 suspension, steering and brake components. The best bang for the buck is probably a lightly modified stock suspension. The most fun is probably had in the complete aftermarket systems. There are a lot of people on this post who are a lot more knowledgeable than I on the details of these kits, and I'm sure you will get enough information that it will be hard to decide which way to go.
You might include a couple of specifics for us to work with. Are you wanting to use a manual or automatic trans? How are you intending to use the car? Any plans to drag or road race? These things will help people give you the best information in regards to parts that will fit your needs.
OH YEAH, and don't miss the sticky on the top of this page that details an I6 to V8 conversion.....and be sure to do a search for some of the other topics too.
