Seen 5500 in 5th before. 225/50/16 rear tires, R154, 3.73 gear. Speedo's been broke for a while, but I know rpms don't lie. :)
Saw over 5k in my SS once, in 5th gear... speedo was damn near buried, and that was with the tops off and windows down, and that car is 100% stock. Scary thing is, it...