According to the manual any semi up to 12000 lbs fifth wheel load is correct, which means for example semitrailer,Stake and Platform, 5 ton 2 wheel, model 516 or semitrailer , animal and cargo, 6 t, 2 wheel Model SKD 1815 or model TG or 32 G or semitrailer , Gasoline tank, 6 t, 2 wheel, M30 (helps filled with gas for at least for a good action radius, when connected to the trucks fuel system) or semitrailer, van, 6 ton 2 wheel by American Body model DF233V, Carter model C15935A, Dorsey model E14, Kentucky model 1-ODR, Olson model KV10, Stick model 400W, Timpte model T8D, Utility model GSW4 or Semitrailer, van, 6 ton, 2 wheel Gerstenlager model W8125 or Gramm model DF-75 or Gramm, Checker, American Bantam Carolina, model STV 620 or Highway model SKD 2181 or SKD 2215 or SKD 2270 or Olson model LV 10 or Trailmobile model B34H or Utility model G-SW4 or semitrailer 7 ton 4 wheel M26 of different makers or simelar models of that time. If you do not use the maximum payload (ex. as a camper), everything in use until the 60's is good for you. Check for the propper air brake connection!
Wolf