I have a 1974 Ford F250 and the tire size for this truck has been dead for a while (31x10.50R16.5LT). Is it completely necessary to replace the wheels to get new tires for my truck? I'd like to keep the truck as close to original as possible.
If you have 16.5" diameter rims, and wish to retain them, then you must match the exact inner rim diameter with replacement tires.
Never attempt to "get by" with a 16" or 17" tire on a 16.5 rims. Similar things were attempted for a very short while when metric diameter wheels were brought briefly to the US, and then stocks of tires vanished with the ill-conceived idea.
The answer is no, heck no, bloody heck no. Sorry. Super nasty results await anything but the correctly matched inner tire diameter. Completely unsafe!
However, as the above posters mentioned, there's still availability of the old-school size scheme, albeit terribly limited. 16.5 was an almost-medium truck size in that era that never really caught on. [sigh] It's either new rims (but you could do some nice aluminum mags from Tire Rack with tires quite reasonable, and keep the stock steels... or it's the dwindling choices in 16.5" tires, Sorry the news isn't better.
looking at tire rack. Searched by rim (wheel) size. Came up with 3 results.
The 9.5R16.5 looks somewhat close in size at 30.6x9.5.