We do offer just the king pin like the Buyers Products 2" Forged SAE Trailer King Pin with 1/2" Bolster Plate # 337KP20050 which gives you the standard 2" king pin for use with a 5th wheel hitch.
It is a good idea to have a qualified welder install the king pin, as the welds need to be sound to support the weight of the trailer.
I included a video of the Buyers # 337KP20050 for you to take a look at. view full answer...