You might need to ask Cass ( DoctorDiff ) about that. I have a feeling that the actual booster is the same, if you are referring about an ebody. The difference may be in the way the rod on the master cly side of the booster is adjusted to length. The drum booster and disc master are different on a b body. The single diaphragm midland Ross is not as strong as the dual diaphragm Bendix used on the disc brake system.