I'm looking for extensions kcamath.mfx and overlay.mfx for Fusion 2.5. I have the .cox versions for both of them and thought I might be able to convert them. I downloaded overlay.mfx from DarkWire but I had issues with the .exe file. MMF2ExtPatk2 contains kcamath.mfx doesn't run on Fusion 2.5
Where there is a CF2.5 version it is usually available via the in-Fusion extension viewer (e.g. Advanced Math object).
Without the source code you can't convert old .cox files to work on CF2.5, but you can add the files to a folder to still be able to run your \Extensions\mmf1\ folder.