colad, looks like you have several ways to tell the difference. If you have the oil pan out and can take it to the parts store, you should be able to find the right gasket by trial fit. My only added advice is to go to a parts person that knows something about Ford motors, like some of the posters that have replied here. I've had the same experience buying parts for my Bronco's, and often have to ask for a particular salesperson. Most will just go by what the computer screen tells them and don't have a clue. Good Luck!!!

 

My 90 Bronco and my 91 F150 both have 5.8L embossed on the upper intake, check the VIN plate, should have an H (the 8th digit) if it's a 5.8L, if it still has the stock exhaust it will have dual tailpipes exiting on the passengers side behind the rear wheel