As per Coan - "A spragless converter will never be faster than one with a sprag, but that doesn’t mean a sprag is always the best choice. Often times a car with a high horsepower-to-weight ratio can run both converters and see negligible difference in performance. For this reason spragless converters are often favored due to superb consistency and durability."

I don't disagree with this. If I were doing a Stock-Super Stock car, it would have a sprag. Bracket or throttle stop class, spragless.

Stall speed around 1200 less than max RPM. Stall speed is one part of the equation. 2 converters, same WOT stall but with different internal set ups can work completely differently.

727 efficiency? Lightweight parts and roller bearings. The best units today are the Pro Trans trans built for Hemi Super Stock racing. 7k+ new, but they are around used. Maintenance would be more of an issue on one of these. Any of the Mopar trans guys can help, but expect to pay a premium to gain a few tenths.