Everything I have found on them is that they are right hand drop cases, and most use the 8 bolt racetrack pattern. I believe they are the same, but there may be some differences I am not aware of. There is also a rare 6 bolt round pattern, but they are very hard to find.
They also use a 23 spline or 29 spline input shaft, so they won't match with any of the normal GM tranny's.