When you decide to convert a six-cylinder Mustang to a V-8, what do you need to get the job done? First, you need the vehicle, engine and driveline, brakes, and suspension to be cohesive. This means you cannot and should not do it half-way and on the cheap. In other words, don't just drop a V-8 into a six-cylinder Mustang without changing the rear axle and all underpinnings.
You're also going to have to decide what you're going to want from your Mustang when the conversion is complete. Be committed to what you want the car to be and stick to that plan. When you don't, it gets expensive. What's more, do your homework ahead of time and know what will work well together and what will not.
Here's what you're going to need in a nutshell: