I can tell you what you would want to get off that car, the whole rear disc break assembly
Because thats what I want if I have access to a wrecked GTS.
If he got into a wreck where someone hits him or he hits someone DO NOT GET THE ENGINE PARTS OFF THE CAR IT IS VERY UNRELIABLE!!! It may look ok from the outside but you can not see any hidden cracks or whatever.
If he rolled the car where there is nothing but exterior damage then you can take his engine... but then those damage is never considered totaled just need a lot of body work.