There no RV-specific tire in that size, nor in the metric/radial sizes for the HD 16" wheel that replaced the commercial truck 16.5. What you will be looking for will be a LT, in Load Range D or E.
Not many manufacturers still make tires of any size for 16.5, not even Cooper, who once sought out these smaller market niches, If the only Transforce you can find is 8.75, you need to find out whether there is clearance for these (particularly dually spacing).
I would be inclined today to look for an upgrade to more modern rims, it is usually easier for a Chevy of that vintage than for a Ford, because GM made the transition from 16.5 to 16 while still using lug centering, changing over to hub centering (where hole size is critical) somewhat later.