The line pressure was a little higher on the Jetfire transmission. I am not sure how they accomplished this. One thing for sure you need to do if you rebuild it is to update the original aluminum governor to the replacement cast iron one. If you can’t find a cast governor I have an extra.
For cleaning the case, We soda blasted mine. It turned out real good. You can also spray a cast aluminum paint on it VERY thin. So thin you can still see the aluminum under it. This will make it look very nice and can’t tell it has paint on it.