I'd recommend selling the AMX, it's a rare car and hard to get parts for. The Demon seems to fit your need to accommodate your family and A body parts are still fairly plentiful. Which one is going to be harder to replace if you crash it on the track? If you want to build a hardcore track car then sell them both and buy the best Viper/Corvette you can afford, gut it, add cage, brake upgrades, and let it all hang out.