Keep in mind what it says on the hitch isn't necessarily what the truck is rated to tow. The factory hitch on my 2500 Suburban says 10,000lbs, but my owners manual says my truck is rated for a maximum 6,000lbs with or without a WD hitch.

Either way, regardless of hitch type, you don't want to exceed your truck's GVWR.

 

I have HD payload and max tow, and my hitch also lists 500/5000 lbs (tongue/trailer weight) for weight carrying.
A correctly adjusted WDH will distribute about 20% of the tongue weight back to the trailer axles, but then you'll need to add the weight of the WDH itself (150 lbs?), so it's probably about a wash in your case.
Yes, you'll be close, but probably okay if you load everything else inside the trailer. I would take the rig to the scales when ready for camping.
And never believe anything a car/truck dealer says about towing, towing limits, towing safety, etc. Never. Ever. LOL, really, I am not kidding!

 

Hu, crazy! It's funny because my 87 Toyota's bumper pull is rated for 350lbs and 3500 max towing. You would think it would be much more on a 2012 full size pickup with a hitch mount... Lol

 

It actually IS much more - 43% more. What's the difference in the weight distributed limits between the two trucks? Probably more, right?
The issue with non-distributed tongue weight limits is not necessarily the strength of the hitch or the vehicle itself, but maybe unloading of the front axle which can cause unsafe situations.
Why are you concerned about the weight carrying limit? I thought you were going to use a WDH anyway?

To answer your original question: air bags are usually not needed for travel trailer towing as the WDH should take care of the sagging. Now if you add a lot of weight in addition to the truck bed, then maybe. But you may want to check your payload limit.

I would bet that your 630 lbs dry tongue weight will be north of 800 lbs once you add a battery (50-60 lbs?), propane (50-60 lbs?), any trailer options (A/C?) and cargo plus fluids in the tank(s) and water heater. Now with the 650 lbs grizzly in the bed, you are at around 1,500 lbs without people or anything else, probably near your payload.
If you want to load and tow all of this, you probably would need air bags to keep the rear of the truck from hitting the bump stops all the time, but the real reason is that you'd likely be over your limits. In the end, only a trip to the scales would tell you for sure; right now we are all guessing.

BTW, I believe any trailer connected with a ball hitch coupler to a ball is referred to as "bumper pull". It does not necessarily mean that the ball is directly connected to the bumper, it can be mounted to a hitch under the bumper also like with our tow packages.

 

If you require airbags, to correct a sagging rear axle with a WD hitch, then you do not have the hitch set up properly.

A WD hitch is designed to distribute the hitch weight pretty well equally across all axles, including the trailer.

 

A WDH should only be used to distribute the tongue weight of the trailer - and not to compensate for weight in the truck bed (like the Grizzly in this case). You are right if you are talking about the trailer tongue weight only.

 

Yes, and that is why I was wanting to get air bags, set up the w/d hitch with loaded camper only. Then load wheeler and use the air bags to do the rest.

 

You will most likely be over your GVW rating with that. Just saying, up to you to decide if that's a good idea or not.

 

My airlift kit is on the way. should be here friday. Hoping to install them on monday. along with some new LED lighting inside and out.

I had airbags on my superduty. I really like how they assisted the leaf springs and made the truck feel so much more stable. That is why I am adding them to my F150 now. But as advised.... they do not increase your payload or GVWR.