Hi. Congrats on your purchase
I would certainly wait for the camper to see the actual sticker weight off the factory floor if you don't already have it. We bought a 2013 Sandpiper 365saq. EVERY dealer website we looked at listed the weight of the unit at 11,873. Including the dealer we bought from. This is generic Forest River factory info for the unit line. When our camper actually came into the dealer the off factory floor sticker weight was 12,721. Almost 1000 lbs more than advertised. Obviously you add second AC, corian counter, slide toppers etc etc. the base weight will quickly rise.
On another note. I pull with an '08 f350 Crew Cab Long Bed SRW. I have not weighed but I'm sure I'm approaching 14k with the camper loaded. The camper pulls great! They are heavy, and they are long but pulls very well. You may need airbags I'm sure and I've never towed with a dually but in my opinion the SRW can handle it fine. I know many experienced truck and camper guys who tow huge units with SRW trucks with no issue. This is my first 5er after having a TT and a popup before that. It will be daunting the first time you lay your eyes on that 42 footer especially after pulling a popup. The sheer length and height add to the initial shock. However, I think you will be more than pleasantly surprised at how it tows. Rock solid on the road. Do take some time on some quieter local roads or an empty lot to get the feel for it tho. Height will now play a much bigger factor for you now too. Also, and I'm sure your model is the same, my SAQ has a 14ft cantilever behind the rear axle to the bumper. Just something to be aware off. You get quite a swing on it tight cornering or navigating some off the tighter campgrounds.
I hope you are getting some good advice. I think you are and have done your homework.
Most off all I know you will love the 5th wheel experience. Everything gets easier. From hitching to setup.
Good luck with it and keep us posted.
2013 Sandpiper 365SAQ
2008 Ford F350 Super Duty
6.4L Powerstroke Long Bed CC