After getting lots of very helpful feedback from people on this forum, I forked out the dough for a four new Michelins for our 1992 25' Excella.
I went with Michelin LTX M/S2 P235-75-R15 XL 108 T.
It says on the tires that they are rated to carry 2183 pounds. Interestingly enough, the dealer looked up their load capacity and his information said 1985 pounds. I also saw 1985 pounds listed in several internet sources. I was happy to see 2183 on the tires themselves just like some posters said I would. That leaves me plenty of margin since I'll only be carrying about 1500
pounds on each tire.
I haven't mounted them on the trailer yet, but am anxious to get them on the road.
Now on to new tires for the F-250 diesel, but that'll be a different thread.
Thanks to everyone for the helpful posts when I was figuring out what to get.