The difference between a 6-6 bed and the 6-4 bed of the Ram is only 2". Compared this to the 148.9" wheel base means you will only loose about 50# more off the front axle by moving the camper back 2" (assuming a 4000# camper). If that is going to through off the handling, you have more things to worry about.
If you are worried about it, go long bed and mad extra storage in front of the camper.
FWIW, I have heard of some handling problems associated with the 2014+ 2500 Megacab with the rear coil suspension (coils are located too inboard aggravating sway). Heard of no issues with the 3500 megacab SRW or DRW. Both use leaf-springs on the rear axle.
This is true and caused by two main factors. One is the coils provide no resistance to movement so tends to lean and bounce a bit more. Other is leaf springs are located outside the frame while the coils are located inboard of the frame meaning the leaf springs have a wide stance for improved stability.
On a side note, the 2014 and newer SRW trucks only have a main spring pack. The DRW trucks have the a main spring back and a helper spring pack.