8.25 build

Sweet duster. Pro gears? Are you referring to manufacturer/quality.
Richmond's gears in the 4:30 ratio is recommended for racing. (Not the ratio but the ring and pinion)

Ill have to check on the 3:73 ratio but I do recall they are Usa made.

Im leaning towards the 4:30s as most commandos and d/darts ran a 4:86 out back. I'm just a little concerned my first gear(3.09) with the aluminum flywheels and my car being real light a 4:30 might cause more of a traction issue or run out of gear if I take it down the 1/4mile.