Pics of My 77 Dodge Vandicraft Class B & a Tire question...

I'm running Kelly tires on my unit. They were on it when I got it. My unit looks like it's sagging in back but the levels all say it isn't. The tires have a lot of life left although they may get replaced come spring if I still have it. I'm torn between keeping it and getting a trailer. A trailer will have more room inside but not the ease of moving.