Will need Bags if I get a new 05. I have a 38.5 Rampage toy hauler. On my 02 2500HD I needed them. If I get a new truck will I need them or is the 3500HD dully handle the load without bags??

I transfered mine from an '02 2500 HD to a new 3500 because I tow a 15k 5th. wheel trailer. Keeps the bed level. The old brakets bolted up with just a couple of minor mods---nothing major.

moving to suspension....

Air Bags are always a good idea because they allow you to keep your headlights level. You may not need them on the 3500 as much as you did on the 2500HD, but the 3500 will still settle down some in back with a heavy load.

2004.5 2500HD LLY CC SB

I don't think you will need them. I had them on my 3500 SRW, and never needed them with 4k in the bed ( camper) Now on my DRW 3500 I went without them and it sits perfectly level with 4k plus in the back.

I have them on my 2002 2500HD which is basically a 3500, and also added them to my 3500. Need is one thing, benefit from having them is another. I am certain you will benefit and as mentioned above headlight aim is a big plus...