I do not think the gears had much to do with your loss of ET. Last year I had a 380 HP 360 crate motor in my D-50.Ran a best of 7.46 at 91 mph with 5.14 gears changed to 3.50 gears and ran a 7.60 at 90 mph.

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1.33 60 ft,6.21 at 110.59 in the 1/8, pump gas small block,2950lbs,drag radials,mufflers and driven to track ...