I'm looking to get a intermediate shaft bearing modification done to the case involving welding and machining the bearing size bigger (as has been done before on this forum). I do have a number of 555 cases, but the case I have handy has a hole punched into the bellhousing from a previous clutch mishap. So I went to my cold storage to get another case, and in the darkness I didn't notice the case I grabbed was from a dis-assembled 520. I can go back to my cold storage and forage for another case, but it got me thinking. (long story for a short question).
So...Is there any real difference between the 2 other than the alleged heat treatment the 555 supposed to have? The assembled trans would have 100% 555 parts in it. Obviously I don't want to spent all the time and effort to find out it wont work with my internals.