I posted to your T2499 questions on the other post.
Now to your question here. In 99, GM did not do a great job in the truck manuals on towing ratings. Around 2004 they did start putting these kinds of things in the manual. That said we can back into what your truck can hold up as far as trailer tongue weight. You need 2 ratings to fit.
1. The actual receiver rating on the back of the truck (the hitch some times called.) It has 2 ratings in most cases, weight carrying and weight distributing. Often times a sticker is on the receiver itself.
2. The actual remaining capacity of the truck rear axle and available GVW before you reach GVWR on the Burb.
Both items create what tongue weight your truck can handle.
Does your Burb have the factory installed receiver? Your 99 would look like this. It has a square tube as the cross tube of the receiver. This is what GM put on that vintage on the pick ups and the SUV up to year 2000 then the receiver changed. Looks like this. This one is off a pickup. It may have a higher rating then the SUV but still look the same
If someone added an after market receiver, it may not look like the stock GM one but it should have a rating sticker on it. The sticker would look something like this. This is a 2007 Burb
Or this 2003 Burb
Tell us what that sticker on yours says for weight carrying and weight distributing. Then we have to back into the rear axle ratings and GVWR. On your driver door sticker there should be a GAWR-RR for the rear axle rating and a GVWR for the gross truck rating. What are they? After those rating we need to figure out the truck unloaded weight front and rear axle.
To this question
Is 7300 with WD hitch, and if so, what is ball-only towing capacity?
Your truck or most any truck in the small weight classes will be able to pull more weight and hold up more tongue weight when using a weight distributing hitch. Meaning to get that 7,300 # pull rating, the truck must be empty with the exception of a 150# driver and full fuel and a weight distributing hitch.
Odds are high, you are only rated for 5,000# towing with maybe up to a 500# tongue weight in towing on the ball with no weight distributing hitch.
And GM use to rate the truck tongue weight at 10% of the tow rating. Which means it "might" end up having a 730# tongue weight when using a WD hitch. But again that is with an empty truck. If you load up the back of the truck with gear, it will subtract from the available tongue weight capacity.
Look in the truck manual under towing and or tongue weight. By chance GM may have put it in there. I will see if I can find and online manual to help.
I know this all sounds, how can it be that complex, but it is all part of understanding the truck ratings. "If" your truck was rated to be able to have a 730# tongue weight, that means the rear axle can hold up the 730# when using a WD hitch, but it also means the back cargo area of the truck is empty.
Get us some info and will try and help you narrow this down
Hope this helps