All the running gear from a 2wd saff coswroth will bolt into a 3dr non cosworth shell, but the gearbox mount will need to be modified, its not a straight swap over, the 3dr non cosworth shells have different mounting points so you could not even use a 3dr cosworth mount instead of your saff one - just to clarify the 3dr cosworth one and the saff cosworth one are different shapes entirely.

at the rear you will also need to modify the arb mount as these are also different, some 3dr non cosworth shells had arb mounts but these were outboard like on the 3dr cosworth but the 2wd saff cosworth is mounted inboard

It can be done, and not that difficult but will need some tweeks to work