As others have said that flexplate will not work. B&M discontinued the 360/904 internal plate, I don't have the old part #. The outside diameter of the one you have can be cut down or you can buy a new SFI plate from Turbo Action.
A close friend mentioned that option to me of machining the current flexplate, do you see any risks hereof in terms of plate disformation etc?
Any references, partnumbers to turbo action Flexplate?