You can make any motor fit that you want, they pretty much all require motor mounts to be welded in.74260z said:
Most people opt for the auto trans because it's easiest to drive. It may also be harder to get the stick where you want it on a manual. Putting a 350 and a T56 in a 240Z would probably put the stick shift way far back of where it would have been originally. Since autos are mostly selected by cable or adjustable metal rods, it's easier to install.