They were never 100% identical, but will fit each other, there were 5 different makers of tanks supplied to ford, the later pattern "MADE IN CANADA" ones are ok, the best ones imo were original kit early sapph, the swirl pots were made by a mercedes subsidiary and worked ace.
In short a 2wd and 3 door tank will replace each other no problem, externally they might have different bulges/ribs etc but will fit no probs, though you may find on some pattern the main breather that goes from the tank to the filler neck needs a extra inch or so rubber extension, this is about 1/2 diametre, opa or fuel pipe etc can be used, note this is the breather not the main filler which will fit no problem as it sits a long way into the tank.
Make sure it has a swirl pot, can see through the float hole, or see if it has spot weld marks around the 10" diametre round metal shape underneath.
tabetha