Here is a rim manufacturer's specs for a rim appropriate for ST235/85R16F or LT235/85R16G. All 16" LRG light truck tires have a single rim width of 6.5".
So, the basic answer for rim inflation pressures and load capacities can be identified by their manufacturers. As seen in this reference, rims are certified by SAE. The FMVSS directions to trailer builders is to use rims appropriate for the OE tires. Tire manufacturers are required to provide the sizes. Specifications for load capacity and pressures are not required to be on the rim. When not there the rim manufacturer must provide them on request. The rim manufacturer is also required to properly identify each rim, by serial umber, part number or both with a permanent ID tag or rim markings.
TR8 | Sendel Wheels
p.s. FR may drag their feet on a rim spec request because they already know the rim is marked with it and sooner or later the owner will figure out where the markings are. Look inside the rim and somewhere on or in the spokes.