All depends of the budget you are planing to spend on it. There is no need to have a name like Foose or Rad Rods, sorry Racedraper :-), to build a car with high value.
Look at the Ring Brothers, they were unknown until they built the Kona Mustang
. They started from a regular 1967 fastback and the car sold at over a $1.000.000 on Ebay wich is a price that no Shelby, Boss 429 or other rare original Mustang ever reached.
There is no need to go that crazy but if you modify your Mustang with taste and quality parts, your Mustang won't loose any value.
The latest craze in Muscle cars is the Pro touring style. Classic Muscle cars with modern technology. I love them.
To learn more about them you can visit this site: Lateral-G.net