I have a Curt A16 on a R16 Roller ((#16521)=16520+16560) and a Double Lock EZr gooseneck hitch to 5th wheel rail adapter (#16220) for sale.
$625.00 for all three, or I'll sell them one piece at a time. PM me for more pictures and details.
I'll deliver them free within 175 miles of zip 36545 (Jackson, AL). Will negotiate longer distances.
I'll even throw in the homemade fifth wheel lifting adapter.