Perusing the website, there are two E4OD packages, a Heavy Duty and a Super Duty. The built transmissions do not give a power rating but the Monster in a Box kit descriptions say they use the same parts in the kit as the transmissions they build, 500hp/450 torque. Cost is $1800 without a torque convertor
Ford 7.3 diesel stock makes 450 torque, so it sounds like the transmissions are just like the average transmission shop's HD rebuilds, nothing special. A real 500hp 7.3 would be making around 900-1000 ft-lbs torque, twice the rating of this transmission. The warranty period of the transmission is very short.
The stall speed of the torque convertors they sell is 2300 rpm, sounds high to me.
In other words, it ain't a BTS.