It would help to know the engine code of this V plate saab (im assuming you mean circa 1980 because if not then id not even bother with it). I assume its what would be known as a B motor, however it could concieveably be a later H motor.
to be honest its probably better if its a B motor. I dont know where you got this light pressure idea from. they run at about 1 bar of boost standard (I have 2 old origional saab turbos (99's)).
Also the reason they have a lot of leg is becuase compared to say the turbo out of a 1.8t they are massive, its old school power here too so theres no variable vanes.
In the USA its not uncommon for the turbine blades to be cut down so that they spin up a little faster, they can still achieve some respectable boost figurse like this.
Also these 'old saabs' do run k-jet so if you were gonna do the conversion you could rob the car of its injectors etc, which are higher lflow than the standard ones you have.
As for the problems with compression, you could always get a big copper head gasket made up to sort the compression ratio, I dunno how thick it would need to be but id want a hefty 1 if i was doing it. youll probably need quite a bit of head work, and things like sodium filled exhause valves too, and of course a manifold thats up to the job.
It sounds like a bit of an ambitious project but anything is possible.
As for performance its hard to say, saab managed to engineer crazy figures from their rally spec turbo cars and theres a nutter in sweeden who a while back was running his saab turbo with 4 bar boost, so i bet that wasnt exactly slow. even at the standard level of boost tho (if the motor could take it, id be worried about the bottom end!) it wouldnt exactly be slow >3k rpm.
at the end of the day its down to you.
I may be able to offer some insight into whats on the saab in terms of bits if you can provide some more detials.
Dave