Passon Performance 5-speed
Passon does have an overdrive gearset available for a standard A-833 case. That conversion changes the ratios around and makes 3rd 1:1 and 4th the overdrive. This gear set is around $1900 last time I looked. That's an option that I am leaning towards because its less than half the cost of his 5 speed and uses all the standard 4-speed parts just like a stock trans. And the ratios are adjusted to even out rpm drop between shifts.
I know thats not what you are asking about but I just wanted to throw that out there.