I think there are a few older 'club' cars that could be built into 'period' Sports Sedans and why not? All you would need is a process whereby an owner would notify their intentions on how they would modify the car and the committee could let them know if the car would be eligible in that form. I reckon that with a few sensible rules that don't allow 'new'-builds to overshadow the cars we're trying to coax out of retirement, this could be a hugely successful class.