Which bags on my 55?

[TINKERDUKE]

I'm gonna be bagging my 55 tf half ton step side this winter. I've done quite a bit of research and have decided on slam specialties re airbags (which I plan on getting from Travis at azperformance) but need to know which size gives a good ride. I'm on a camaro clip and will be adding a 4 link rear setup with the bags just behind the axle. The truck will be loaded with all sorts on a regular basis and will tow a large trailer sometimes aswell.
Hoping to order soon so any help would be cool
Steve.