Wouldn't worry about it at all. We have a 2012 Forrest River Lexington 283TS on a Ford E-450 chassis and absolutly love it. We tow a Subaru and don't even know it's there. Rig is probably same size as the one your looking at. The 250 would be even less weight/size on the same chassis.
Neighbor has a 2005 Thor 4 Winds, 31' on the same E-450 chaqssis as the ones your looking at, again with no problems. There are thousands n thousands of class c and b+ motor homes built on the E-450.
Think about all the rescue vehicles, ambulances, and other commerical vehicles you see daily. Almost every one is on an E-450 or F-450 chassis. There's a reason--they hold up. When's the last time you saw such a vehicle on a Dodge or GM chassis? Probably during the last blue moon.
Grumpy