Aren't the boxes smaller on the old mega cabs ? Should not be an issue as long as you are not pulling a trailer ?
Good thing it's a 3500 as. 2500 Are pretty much useless a deck with 2 sleds,gear and 2 people would pretty much put them over legal payload
I have a 2500 mega I put two sleds and gear and people in it every weekend haven't had one problem yet airbags and removed the decals you would never no it's not a 3500 and went on scale still have wieght to spare, I have a cross trax I had it on my 06 and now it's on my 2011 same size box.