i have oil in my coolant , where could it be comeing from on 1991 Ford Ranger

mechanic checked and said it could be caused by the therostat housing is this possible and how to id and repair

2 answers
seek a 2nd opinion. did you over heat trk at all?
check to see if you have oil cooler lines going into the radiator. if so, the radiator may be damaged and need replacement.