So, are you saying Ford engineering and building abilities are inferior to your own? How many cars have you designed, built & sold?
Having modified and bastardized damn near every aspect of a car that could be done, I offer my very sincere, experienced point of view with you best interest in mind, not mine. Many decades ago, when I was 16 and asked this "old" middle aged coworker whom had converted a automatic car to a manual transmission car for his assistance on my project doing the same, his response was quite frustrating to me. He said No he would NOT help me with the project, and that if I wanted a manual transmission car, I should buy a manual transmission car. (Keep in mind, they DID NOT sell kits for such things back then). I was upset and somewhat insulted by his reply and advise. I did that project, and eventually a second one too, and eventually learned, what he was trying to tell me in the first place, in retrospect, he was dead nuts on with his advise.
If you want a V-8 Mustang, buy one that came from the factory that way.
The acronym KISS really does apply here. The vast majority of backyard engineering can't hold a candle to Fords engineering.
Yes you could put an engine together, just how you want it, but why do that with an old body that will then need all new cooling system, suspension, transmission, rearend, fuel system (?), wheels, brakes, engine stands & mounts, exhaust system, etc, when you could simply build an engine to your liking, and put it right into a complete fully functional factory V-8 car?
Here is a prime example of what all of your blood, sweat and tears will amount to in the end, a highly bastardized car that isn't worth what the original unmolested one was.
Besides, your analogy is a little off, working your ass off, saving your hard earned money and buying the car you want is not having it given to you...