2009 Weekend Warrior pin box/ frame question.

I apologize up front if this has been answered somewhere before.

I have a 2009 CR3705 5th wheel toy hauler. I am converting it from 5th wheel to gooseneck.

I really like the gen y hitches, as well as the shocker.

My current pin box is a Fabex 765, BUT, I am told this is not factory, and that mine was converted to this pin box by a previous owner. Likely to shorten the length of the pin box.

I was told this by weekendwarriorparts, and when looking at the setup, feel inclined to believe it.

I was told that factory pin boxes were lippert 1621 or 1121.

I have no way to know at this point if mine came with either of those, but suspect it did.

Does anyone know what these came with standard?

There are extra holes where the pin box goes.

I am attempting to get a build sheet for the trailer, no luck yet. Leads on that also appreciated.

Thanks for any help.