I have both the front and rear 5th wheel assemblies from a 500 series and will fit a 400 series and possibly others. They are solid aluminum. The rear has a solid plate welded to it for extra strength. $200 each or $350 for both. These are very heavy and I could probably get that much for them at the recycling center. They are located near Tacoma, WA. I will not ship. I could drop them at a shipper for a small fee if you make prior arrangements with the shipper including crating. Contact me by private message if interested.