1977 904 horsepower limits?

I have worked on a couple of 904s and now have a 1984 # 999 trans listed for a non lockup hi altitude 318. I pulled it apart today. It is a BRAND NEW old stock trans right from dodge, factory tag, caps and plugs still on it. 34 years of storage put a touch of rust on a couple of clutch retainers, the bottom of the oil pan and exterior pump surface , but that is it! There was enough oil in the pan to protect the valvebody.
Best part of this it has the big, wide 5 clutch drum, steel planetarys and the 2.76 gear set! So it has all the good parts needed to build a trans for my 408.
It will get new clutches that hold better, a solid kevlar 2nd gear band, forward manual valve body. The manual valve body runs high preasure all the time, and higher than max stock.
A stock trans fails due to low pressure that a stock unit is set to run, and is hog tied by the linkage system. A stock type linkage that regulates pressure would not increase the line pressure at part throttle enough because a bigger carb on a bigger motor makes a lot more Power for the first part of throttle opening than the linkage provides. MUCH more than a stock 2 bbl 318.
In 1977 the 904 was transformed into the 999 by drastically strengthening the front clutch and planetary systems. It was done to allow use behind a 360 in a heavy Fury car.
The parts for those trans are what it takes to survive behind a 408, as i understand it.