[ByronRACE]

Try a google search for "allison 250 for sale", or "T63-A-700 for sale" and you'll find a long list of resources.

The best deals on these engines are the military surplus outlets where they sell pull outs on pallets. When they come available, they usually have a detailed service history and are removed well before they reach end of life. In a car, you are safe to continue using a turbine with little consequence right up to the end of life. In an aircraft application, they swap them early. If you look around on the turbine jet boat build sites, you'll find the jet boat guys put tens of thousands of hours on these turbines and continue to operate them well beyond the end of the recommended service interval. They run pretty much forever as long as they aren't over rev'd or suck up debris.

The biggest issue I see in running a turbine car would be noise, fuel consumption, and exhaust heat...in that order. You'll spend considerable amounts of time addressing all three issues, but the end result would be pretty cool; definitely a conversation piece. Practical, not at all!