Many older hitches didn't bolt to the trucks frame rails. My 1st hitch was a 12k Atwood sliding bar jaws that was bolted to the wheel wells and framing under the bed. Remove two pins over the wheel wells and the whole hitch came out.
They were what they were for that time and era.
I would get dad a modern 4 way pivot hitch. Those old hitches didn't articulate side to side were bad about getting a pin hung in opening ....especially when the ground has the truck/trailer in a twist. I carried a pinch bar and crow bars as we camped in lots of primitive camp areas. A hung pin is frustrating the first time it happens.
A 4 way pivot hitch eliminates the problem.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides
