Some other items are also somewhat misplaced, like three-fingered insulated gloves (/obj/item/clothing/gloves/nabber). Probably caused by the fact, that GAS has a slight sprite change in the past.

Steve mentioned, that some of these issues can be fixed by using the same sprite offset system that is used to make backpacks fit GAS, but I have no clue what that system is and how it works.

Also, some of the new hazard vests are misplaced on GAS:
/obj/item/clothing/suit/storage/hazardvest/yellow

/obj/item/clothing/suit/storage/hazardvest/red

/obj/item/clothing/suit/storage/hazardvest/purple

/obj/item/clothing/suit/storage/hazardvest/med

All other (older) hazardvests are sprited right, like the /obj/item/clothing/suit/storage/hazardvest/white:

There may be more hats and overwears that have misplaced sprites, but from the ones commonly used, those are misplaced, and I don't really know what else than hazard vests, caps and ponchos a GAS can wear.
I can only say, that all ponchos in game fit GAS right.

Also, when hands are stained, front and back sprites are mismatched, but side sprites are correct.