You can't "save" the pushbutton transmission to use it with a v8. The bellhousing part is completely different. You can round up a pushbutton V8 904 transmission and save the pushbutton shifting though.
an LA adapter plate for a slant trans. I know they made a slant to LA trans adapter for trucks and taxi. I think you could possible make the push button work on an A-904 but I have no experience with push buttons.