The cast iron case uses a press fit (more like a tight fit) counter shaft and a half moon key that prevents it from rotating. The Aluminum cases used a floating counter shaft and are different.

When you get the case make sure they include the counter shaft to support the cluster gear and the half moon key for the end of it.

The bearings and pretty much everything else in the kit are pretty much the same. There were early and late style synchronizers. You will need the late style but Brewers will know that.

When you get into it.

1. Inspect the inside of the cluster & other gears for galling.
2. Inspect the interlock levers for cracks.
3. Inspect the small teeth on the synchronizer sliders & gears for rounding or wear.
4. Inspect the flats on the shift levers & Shafts for rounding.

Those are the most common wear items.