why dont you just simply make your own adaptors to fit the calipers. Measure it all up then make your self a nice template out of some stiff card then convert that to a piece of thin sheet steel. Once you have a nice example in sheet steel pop into your local engineeering shop and ask them to make a pair for ya and they could even cut some threads in them for you to bolt the calipers to. I have done this before with cars when converting them to bigger discs.