I agree that Mustang is a Craigslist fail, $50K for a base Mustang with some mods. While some of the mods are good choices, this person has overspent on modding their car and is trying to recoup their money.
If I were in the market for an S550 Mustang (not that I need another one) I could get a GT350 for the same money that he is asking:
https://vancouver.craigslist.org/van...249344398.html
Buy a GT350 for the same $ as he's asking you get the 5.2L flat plane crank Voodoo engine, a way nicer interior and a car that will hold value better than a modded base S550.