Spragless is more suited for 1000+ HP cars that have problems breaking converters. Spragless run hot and are slower, but the 7.9 8.9 9.9 throttle stop racers don't care because they don't run all out anyway.
The newer diod/sprag converters these days are much more durable than the ones of just 5 to 10 year ago.
If your car sees any street time steer clear of the spragless.
I'm going to guess that Transmission Specialties recommended the spragless ?
