I don't own nor have handled a 75BD. Looking at the parts banner at the top of the home gunsmithing forum, there are only a few parts associated with the decocker that are different from the 75B. Based on that, I would deduce that installing the kadet slide would work fine.
Having said that, I remember a
thread in the gunsmithing forum about a 75BD and a problem using the kadet adapter.
Because the kadet adapter is only the slide, it can be fired DA, DAO, or SA. It doesn't care how the hammer is staged before being released to strike the firing pin.