We have installed a water cooled engine in a 911,but that was a supercup motor,does that count.I agree however,the street 996 engine is a waste of time and money,besides,it will not fit without other major changes.
Perhaps a late 964 engine,its less expensive than a 993 engine,and certainly has all the torque you could need.

 

If you don't mind, I would like to know more about this Engine swap you did. What exactly had to be done. I have an 87 944 but not an S model, even though when i bought it it said 944S on the back. anyhow. I wanted to do the 968 Swapp too, but someone mentioned how the 944S was best for this because of some confict with all other models conserning the Bell Housing and Torque Tube. Perhaps you can shed some light on this suject.