This is just an opinion from looking at the pics, but I'd start around $4,000 and not go any lower than $3000. I guess it's based off how quickly you want to get rid of it. If it's someone you know that wants to buy it, that might make it easier since they might know the amount of time/money you spent on it.
Normally, you can't base if solely off the money and man hours spent building it. Unfortunately, many people don't consider all the time you spent making the car what it is important. They don't consider modifications such as those to increase value...
If you got 3,000 for it, you could get that 96 t-bird down to 3,000, buy it and sell it for more. Or you could take the money you get from the mustang and put it towards a GT. There are quite a few decent ones around the Ohio area via a craigslist search, lol.
It's up to you...I'd be safe asking $3500-4000 for it and go from there.
Good luck and keep us updated