They are very different cars, if thinking cossie rust is the main bug bear, as well as the age of the car and how it's been looked after, usual rust areas such as rear arches, sills, front floor pan, rust between front turret and inner wing.
You will find it very different to the scoob, a good car in it's own right the scoob, but doesn't give the exciting feeling(to me anyway) seems just another nicely sorted jap car when driving, cossie is a lot more rewarding, esp when in tuned 2wd mode, as you need to drive them in the wet or dry if going silly, take a lot more input.
2wd can be run so much cheaper though, and trans take more power.
The std sierra suspension at the rear is abysmal but a new poly diff mount and 22mm arb soon sorts it out mostly.
I would suggest driving or at least getting a ride in one before swapping, in both 2wd and 4wd, ideally it would be(for me) 2wd in the dry 4wd in the wet, avoids the brown pants time, having the rear step out at 90mph in the outside lane of a(private) dual carriageway due to too much pedal makes your bum muscles have a workout!!
You defo need a drive they are so very different, scoobs to cossie and 2wd to 4wd.
tabetha