I don't know if it can be replicated as I've not had one in my hands. Perhaps someone else on here will come along that has had one is their hands and can tell us.
As for what the part is called, things are called many different things by people on the street. But that doesn't mean that is what the part actually is. So if you are looking for a part you have to be flexible in what you call it as different people call different parts different things.
Technically the part shown as 17808 in that Ford illustration is not a valence. The illustration I included as well as the part numbers are directly from Ford's Master Parts Catalog. So the part is a DEFLECTOR (REAR BUMPER) in Ford-speak, and they should know as it was theirs. And the part #'s are:
So, armed with the part number you could Google it and see if someone has one. But that is fraught with problems as there are several ways people list part numbers. The way I've shown the numbers above is the correct way as it is cut and pasted from Ford's catalog. But, many times people that don't know better read the "0" in E0TZ, which is a zero, as an upper case "O". So you should search for it as EOTZ as well as E0TZ.
And others that don't know the Ford convention write the part number with a dash, as E0TZ-17808-A or E0TZ-17808-B. And while that is not correct, you need to search for it that way as well because people may list it that way.
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker in front & 10.25 Spicer/Trutrac in back, & EEC-V MAF/SEFI
They have tried to repair it, (it has two rust pieces, broken right thru) and it’s just not the same. The welds aren’t great. It’s so expensive to replace, or even have it rebuilt. Not sure how to challenge this one now ..? This piece is almost impossible to find . And to be a collector, I need to find one.