you can get whole spring packs for less than that from any spring shop. the rv is ALWAYS loaded to the max, that being said, while is says E350 on the side, a cutaway for a motorhome has a larger suspension spec than the regular E350 just as the same year F-super which made box trucks or hotshots were more than the F350. It was not until a few years later that ford decided F450, 550 etc would become part of the lingo.

spring shocks: no help
air shocks: minimal help and almost certain upper shock mount destruction
Air bags: better option BUT, some coaches have a floor brace there (itasca/winnie which make the frames for about 90% of the Class C coaches those years) - ymmv

contact overloads: definite contact with the frame braces and will always be in contact

add - a-leaf overloads: get the best option, but they will ALWAYS be pulled to the max and will re-temper

new-springs with an extra leaf added: best option

installation is not for the back yard guy as a) you gotta lift the coach weighing 8000lbs an additional FOOT and cannot lift from the rear of the frame and you will have trouble getting the shackle bolt out...

 

About 10 years ago, when I worked for a commercial door company, we got a few new E350 KUV's. When loaded with tools and material, the springs had a slight negative arch. This really bugged one of the techs. I assumed it was designed that way due to the fact the the vehicles sat level. He made a big stink about it and when it was all said and done, it was determined the springs were designed that way.

 

BS unless you have a defective mount
I wouldn't waste my time and money on them though