I have OD guts in an iron case in my 68 Charger/440 engine. Did the swap over 10 years ago but not tons of miles on it. (with 4.10 gears the miles are more pleasant) At the time I rebuilt the trans the reading I'd done said the aluminum case allowed the countershaft to move away from the mainshaft and that's what did the damage. The article I read talked about machining the aluminum case to spread the load. Its been a really long time and I cant remember the details. In an iron case with street tires and reasonable driving I wouldn't worry about it.
This article goes through the steps of bushing the aluminum case counter-shaft holes. Not a terrible job if you have a mill. No idea how much a shop would charge you but figure a couple hours on the mill and the lathe work to turn up the bushings. I plan to do this to the one I have.
https://www.hotrod.com/articles/mopp-0110-a-833-aluminum-case-buildup/Does anyone know how much weight is saved by the aluminum case?
