If you want to use the 888 swingarm, you can cut off the lower swingarm mount and reposition the to shock mounting to match the 888 frame. https://www.ducatiforum.co.uk/threa...build-with-some-questions.77793/#post-1628090 If you want to use a 748 swingarm, I am sure the engine cases are too wide.
ST4/4S cases mount the swinging arm the same as a 888 so not what's needed/wanted here. 916/996 motors will drop into a 748 frame and swinging arm. Steve R