I vote liberating some street signs for floorboards like the ole days. Cut the stop sign for the pan under the pedals haha
Ya know....
A beat-to-death looking Mustang (83 at that) with no paint, crappy looking OEM style wheels, tore up interior, with modern driveline, breaks, and 400ish+ HP at the wheels with some sticky tires and ability to pull the fronts?
I'd start painting kill signs on the driver's side door.