I don't think a 33" Toyo MT is going to put much strain on your axles enough to warrant this swap. If you were talking 35's or 37's, then maybe.
If you WANT different wheels, that's another story. I just don't think you're dealing with a weight problem here.
While we're at it, if you are swapping wheels, I'd say go to a 15". That will save you weight and around $100 per tire.