Just another thought but realize that you don’t have access to both of these car or possible either but if you sand or buff through the layers of paint it will likely provide you with what was applied over the base metal originally and what coatings there were - in order from first to last. Done this a fair number of times (wrecking yard owners will stare, point finges and have their comments about the crazy guy cleaning wheel wells and undercarriages ( shops not so much) but a pizza and some drinks normally get them on their way and an invite to come back again. Got to make the effort to get to the bottom of things 