Where are you based DDay.
See here for an example of a rear quarter transplant.
http://www.350z-uk.com/topic/75521-rt-performances-build-on-wassos-car-heres-how-we-did-it/
I wouldn't recommend transplanting a used rear quarter unless it's both layers which needs transplanting in which you can get a clip from the salvage.
But if it's just the outer skin, it is more then likely going to warp or get damaged when removing the single skin off the donor car.
In honesty if your salvage yard is willing to remove just the outer skin, it'll probably cost less to buy a new one because taking it off is a time consuming job.