It’s interesting 3L is a 3.73 electronic limited slip for the Expedition, and then for my 2023 F-150 L3 denotes the 3.31 electronic locking axle. Ford sure is confusing with their axle codes
Unfortunately, the codes are vehicle specific. You know what would be great...if Ford just printed the axle ratio and diff type on the label or vehicle body someplace. A barcode that links to the Monroney would be helpful as well. The dealerships are clueless about HD Towing. There's no way to specify it in a search, so you have to know what to look for in photographs. Interestingly enough, I see more Navigators equipped with HD Tow than Expeditions. Ford made it a standalone option after 2017, so many vehicles were optioned without it. Unfortunately, many of the Navigators with HD Tow don't have a bench in the 2nd row.