My guess would be about 12K-13K ....

..... your mods are clean, and the car looks great, but every car is only worth what people with cash are willing to spend.
But, whoever bought it would need to be a Mustang person....
Ebay would give you some idea...just set the reserve high as hell and see how high the bids go... putting it back to stock wouldn't be fun...
Maybe consider a trade. For what it's worth, I love your car.... it's just far out of my price range.