You will need to fabricate new mounts to fit under the chassis legs, one for the rear gearbox, the sump will need altering as the sub leg hits the corner(thats if your fitting the long legs as yours will be short), than the leg will need a section cut and boxed, part of the engine bay will need some slight modifying as the alternator is too close, you will also need a abs sensor on a leg due to the speed signal in the ecu, you can buy a loom from astra nige on migweb, this will connect straight into the saab loom. What engine have you got?