I just acquired a 1992 240. There are presently no rear headrests. I picked up a couple used, but the speakers on the rear deck, which appear to be Volvo items, block the outboard holes for the headrests. The sockets to retain the headrests are in place on the rear seatback in the trunk, but there's no sign that they were ever installed. So, here's the question: were there 240's in which there were no rear headrests installed from the factory, or am I looking at a cob-job speaker installation on the rear deck , in which the previous owner removed the rear headrests?