Mechanical Diode Converters?

From what I am researching, a transmission converter combination will either use a sprag or a diode. There a lot of people getting reliable street performance from diode converters. The key word I see is not to use a spragless type setup on the street. What was he running it behind and in? It almost sounds like it was for a boosted setup to make use of the low stall stator in it. With the billet cover, is it a bolt together unit? Probably more converter than you would ever need but I may legitimately know someone who needs that for a boosted third gen.