Engine swap - advice needed

Hi all, can anyone tell me what engines will fit into a kz650f2 frame without any modification please? A 750 or 1000 engine would be nice if it drops straight in. Any other makes of bike engine that would fit the frame (honda/suzuki etc)? Any help or advice would be greatly appreciated.

Only the Z750, Gpz 750 and Zephyr 750 will drop straight in on the original mounts with virtually no frame mods at all.
The Z900's and Z1000's will squeeze in but need new frame mounts as will anything else from another manufacturer.