I hadn't thought about E, I'll look into that. Sounds like D is the minimum.
As far as what it came with there is no telling so I'm trying to get a good idea on what the best way to go is. The RV was my grandpa's and while I loved the man to death, tires was not one of his strong suits. We borrowed it once to go camping when I was kid. Dad asked Papaw how the tires were and Papaw said they were in good shape as he had recently bought them. We had 2 blow outs on the way back home on a Sunday when nothing is open. Also we discovered that there was 3 different brands of tires. When we got back Dad asked Papaw exactly when he recently bought those tires and after some thought Papaw said around 10 years ago.