If you have a new body style ie: 2002 and up it is an FL-820S guaranteed. If 2000 and earlier it is FL-1A. 2001 you need to check the what is on the motor. Not interchangable.
I used Fl-1A's on my work 4.0L Aerostars for a number of years. My highest mileage Aerostar had well over 350,000 miles when I sold it and it was still running strong, with no oil added between 5,000 mile OCI's. The next closest in miles was over 250,000 miles with the same result.
We use a '97 Aerostar AWD that has over 230,00 for local work only, but the engine is still in excellent condition. All on FL-A's (or equivalent)..Mostly the real deal.
On the Jeep TJ, it's a real tight fit on the 97-99 4.0 models; it comes real close to the upper control arm at full suspension compression. I stopped using them a couple of years ago due to this. The 00s and up have no fit problems at all due to the filter mount being horizontal.