Rather not use something like eManage really, it's far from ideal.
Fitting new temp sensors is a good idea and resistors to let the ECU think injectors etc. are thisll there too, RPM hopefully could be fed from the new ECU to the tacho itself and if the stock ECU is still retained the speedo, fuel gauge, etc. should hopefully all still work too...
But yeah speaking to someone that knows Saabs is a good shout of course, Saab forum's here I come! lol

Cheers!