My mom put a series of Wheels on the back of her 77 Chinook for the scraping issue. The sagging was so bad that the wheels that were put on broke off a lot. But I think one that worked was a swivel maybe 6 in wheel attached to the frame in the back. If I were to do that today I would just get a wheel That's rated for like one or two tons maybe. Actually I would prefer if my $85 dolphin would scrape I would work on the suspension and leaf springs and maybe airbags. Rather than a sketchy wheel in the back. Best of luck
Pete Wisda