Vernon Morris has the car-to-car FKT for the main trail at "just over" 3h20m set in 1991. Apparently, Morris did the route twice that day as training for the Pikes Peak Marathon and Pikes Peak Ascent combo. He did the PPA that year in 2h34m45s, and the PPM the next day in 4h02m19s.
Whitney Trail car-to-car
3h 20m 30s