So this is on a rolling road dyno right? In the real world it is the air that provies the resistance. Looks like you are right around 138 mph when the fuel cuts off....so I guess you put it in the real world and see how much wind resistance there is. Simplist way to adjust gearing a bit is tire height. Maybe take along an extra set of taller rear tires which would put the top speed at 145 or 150?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.