Tubes in tires not designed for them is bad. It is also against DOT and NHTSA regulations. Yes. there are the so-called "radial tubes", those are not intended for use in tubeless tires. Rather, they are intended for use in tube type radial tires, which are rare these days. The only radial tube type tires I know of are trailer use tires, only used in Europe. I've sen way too many tire failures caused by tubes being run in tubeless tires, and would not suggest it.
As to sizing, the 225/75/16 is quickly becoming obsolete, and the 225/70 is not far behind. We have to special order them as we don't stock them.
