For those that don't have access to the VIN or can't see it, it's simple. Look at the back doors. If the door has a cutout for the wheelwell, it's not an EL. If the door is straight on the back side, it's an EL. To me, the easiest way to tell at a glance is the back glass. If it's long, EL, short glass=not EL.
How I tell, anyway. This also equates to the Navigator L and the newer Max trucks, same principle, just the wording is different.
Here's a couple of pics to help you tell at a glance:
Regular wheelbase Expy:
Expy EL:
You can see what I meant by the wheel well being a part of the rear doors on the standard length truck, and the differences in the rear side glass panels.