Just nosing about on Neo Bros website at they're project cars:

This vehicle was originally a 900 M Reg, V6, which Neo Brothers converted to a 2.3 Litre Turbo in 1998. The following year it was converted to four-wheel drive using a Vauxhall Calibra system. Vehicle has been raced at Silverstone and Brands Hatch.

Has anyone on here done this? definitley makes the idea of upgrading to a NG at somepoint alot more appealing if you can fit it out with 4wd.

That comes up in the NG900/9-3 forum every now and then. I heard that the rear axle is much different and Saab welded some kind of reinforcement back there onto the standard Vauxhall chassis. Still, it can obviously be done, but I bet it's a lot of work.