I'm pretty sure it will fit... I have a T3/T28 hybrid on mine, and that bolted straight on to the manifold. However the pipe connections are in slightly different places and so the pipes will need bending slightly and the low pressure oil return at the bottom isn't a straight link any more and require a convoluted piece of semi-flex. ISTR we got round it by using two bits of rubber pipe with a 135 degree metal pipe elbow in the middle. It's certainly quite achievable.
No, that is a straight T3.
Note that, while the basic center 'frame' dimensions of this are indeed bigger than those of, say, a T25, this does not necessarily mean it supports more airflow. 'T2', 'T28', T3', 'T4' are no more than generic designations for turbocharger 'families'. Within each of them, there is a great variety of 'trim levels' for turbine and compressor wheels/housings available. The T3 on a B202 Saab engine, for instance, couples a .48 A/R turbine section (relatively common) to a 'trim 45' compressor - which at a practical level means it won't realistically support more than about 240 hp before seriously running out of compressor efficiency.
Indeed. As Eric said, a T3 from a stock Saab may be limited to as low as 240 hp. But an "S60" trim compressor can be good for as much as 300 hp. My personal choice for a mostly stock street Saab would be a "50" trim. It's low flow characteristics are near what the stock trim flows, but it can handle between 260-280 hp. Also has what seems to be the broadest efficiency range of the T3 family.
This site shows compressor maps for the entire T3 family. You can also on the same site look up maps for the T04E compressors which are the choice for most T3/T4 hybrids:
Hopefully that will help you in any future turbo selection choice. Good luck!
edit: If you want a quick calculator for how much air a turbocharger can flow ... typically for every lb/min you get about 11 hp. 33 lb/min can flow as much as "roughly" 330 hp. Of course it will also depend on the efficiency of the motor etc, but that's a general rule of thumb that works reasonably well. Try that site's turbo compressor map tool as well. Fun stuff!