These are all good questions. But if you are old enough, "as I am" you'll remember that when these Mustangs were built back in the '80s they were cutting edge.
They were affordable musclecars of their time. LOL Unlike today, these cars were budget hotrods. Ford kept them simple, cheap, powerful for the time, and sold millions of them.
Also they were far superior over Mustangs built from '74 until around '82. Thats when things really started to happen again. An improved 5.0 was back after many years of absence. And actually made decent power for those days. After that, every year offered more power and options.
The SVO's were introduced in '84 and caused quite a stir. They were considered almost "futuristic" with modern/European options such as the inter-cooled turbo, disk brakes, "16inch wheels" have mercy ect, ect. The interior was awesome for that time!
With '85 brought roller cams the return of the 4barrel carb. '86 fuel injection.
In '87 when the aero cars came out along with 225hp/300tq it all went crazy!
Thats when the aftermarket took off and the current 5.0 era started.
As I mentioned up top, These were low cost, strong running, well handling hotrods for the day, cheap and affordable.
Dave,"wythors" Will you believe that when I bought my '88GT vert new it came with a 5yr/60000 mile warranty.