The Commodore A3640 CPU board with a Motorola 68040 was designed for Amiga 3000T and 4000. I have this CPU board in my Amiga 4000.
Information:
http://amiga.resource.cx/exp/a3640
https://www.bigbookofamigahardware.com/bboah/product.aspx?id=250
http://wordpress.hertell.nu/?page_id=514