New to me 5er....hitch recs needed

Unfortunately, I do not know who made the rails. There are no markings on rails. I also see that on the instructions posted by Old Biscuit, the part numbers on the RBW install sheet (page 3) are different from the sticker on my hitch (see hitch pics).

Would these RBW instructions apply without knowing the manufacturer of my rails and also having different part numbers?

Thanks