Without the frames, what your father-in-law has are parts with nothing to tie them together. IIRC, frames are serial numbered parts so are treated the same as firearms and are not that easy to come by. Manufacturers prefer to control the assembly of all parts in their own plant due to the hand fitting that goes into the production of a firearm not to mention the liability issue in having this done elsewhere. Perhaps someone with a FFL can get them but I have never heard of this happening. Frame parts, on the other hand, are not serial numbered so are obtainable without having to have a FFL. That limits my knowledge of this subject and I would appreciate anyone correcting me or adding to this subject.