Didn't you just put a new exhaust on your car? ... and now, suddenly, you're thinking of getting rid of it?
Dude, you're just like me - fix up a car just to where you like it, and then get rid of it.
I got rid of my first Fox back in '02 ('89 5.0 notch T-5) and tried in vain to find something over the next few years that I thought would be more practical and yet anywhere near as fun and easy to work upon. Ultimately, I wound up buying an exact duplicate of the car I had so stupidly gotten rid of, and I had to start alllllll over again with the mods and repairs process. Owning a Fox is like contracting some enjoyable form of herpes in that feels really good when you first get it, and then it just gradually goes away, and later on, over and over again, you have these outbreaks where you love your car all over again (or, if you sold it, you wind up kicking yourself in the nuts for having done so), and it just goes on and on and on. Weird analogy, I know, but that's all I can think of to really compare.
A Fox can be a very practical and personally fulfilling DD car, depending on how you have it set up. Obviously, if you have some insane motor and/or really steep gears or some kind of transmission setup that is absolutely a royal PITA to drive normally and is strictly strip-oriented ... yeah, probably not the best DD you could have. But in stock to at least mild form, a 5.0 Fox (especially a hatch) is overall pretty damned good. With a T-5, you can get pretty good gas mileage (mid-20's highway), they're a blast to drive, they're solidly reliable cars (as long as you stay on top of maintenance, as with any car), they're easy to park, the back seat is actually more comfortable than in SN95 or S197 models (definitely more head room), and a hatch model offers a significant amount of cargo space (not as good as an SUV, but still pretty dang good for a small car).
Sure, you could toss aside the 'Stang and go for something more "practical," but for whatever area that other car can do better in, it will also do MUCH worse in other areas, as well ... almost always in the fun-to-drive category. There are other cars that are faster, sure, and better on gas, or quieter, or roomier, or worth more money, or whatever ... but nothing, NOTHING, offers quite the same driving experience as a 5.0 Fox. THAT is why you will regret selling it and will ultimately find yourself looking to buy one again someday.
Personally, if you feel you MUST have something else for a DD ... I'd recommend just saving a bit o' cash and buying a cheap little beater vehicle of some kind and keeping the Fox as your toy. MAKE room, if parking space is an issue - find a relative or friend or someone that will let you rent a parking spot, if nothing else. (Pretty much what I'm doing with my '89 right now, actually.) Otherwise, just DD the Fox and find new ways to stay in love with it ... usually in the form of mods. Forget about resale value. DO NOT look at a Mustang as an investment or as a liquid resource, as you will NEVER get as much out of the car as you should or as much as you'd want, and almost certainly not enough to justify the loss.
And besides, right now with the economy still being in the toilet and everyone being hard up for funds, you're going to have a HELL of a time selling the car and getting any amount out of it at all, definitely nowhere near your asking price, regardless of what you've got invested in it or what condition it's in. ONLY sell a car like that when you absolutely MUST get rid of it, like if you're totally drowning in car payments (on a Fox? How? Why? WTF?!?) and you just need to get out from under it. If you're doing it just to get a different car, you're probably better off trying to trade someone else straight across for the kind of vehicle you (may think that you) need. Again, you're almost never going to get your asking price for a Fox, so if you think you can get $3,500 to $4k for it, in reality you're more likely to wind up only selling it for $2,500 to $3,000; not only are people cheap bastards these days when it comes to buying cars, but folks just flat out can't afford stuff, anymore, and they're more likely looking to buy a Honda or some other more "practical" vehicle, so you'd have to lower the price to something absurd to really make it appealing enough that they could justify considering the purchase in the first place.
Don't do it. Please. Seriously. You WILL regret losing that car.
