If you put 3.91 gears in it the convertor will be tighter. I put a 3.50 gear in my D50 (Did have 4.56) and the convertor stalled a lot more. At the time it went from 6.34 (4.56 gear) to a 6.39 (3.50 gear)in the 1/8.
I guess the convertor stalling more kept it from not slowing down to much.

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 ...