I'm glad you like your new ride. But if I still think if you have to do that much modification you didn't buy enough truck.

 

Check out these Air Bags, reviews on them are awesome...
1992-1999 Chevy / GMC Suburban 1500 / 2500 - Firestone Ride-Rite Air Bag Helper Springs [REAR] - 2101 | $289.51

 

Something don't seem right with this post - I never met a boat captain that didn't know how big his boat was (38 feet maybe longer?) I think this is a way for this guy to advertise Fords. A 3/4 tons Suburban being put to the ground means this boat must have some serious tongue weight and I just smell BS here. I have had numerous 3/4 ton Suburbans and pulled some crazy loads and NEVER worried about the bumper touching the ground. Post a picture of your boat and truck and I will apologize but I don't think I will need to.

 

In the third post of this thread, based on his OP I questioned if the Suburban was sprung for the load. I got no response. I didn't push the issue because the longer the thread went, the more I was "smelling a rat", so to speak.
If the thread was an honest one, then he's back where he needs to be, with a Ford. Nothing wrong with that, I own a couple of Fords myself, but it seems to me that the thread was more about how much better his Ford was than his Suburban, if the Suburban even existed, at all.

In any case, The Excursion is no slouch I had a Power Stroke Excursion 4x4, and it was a damn fun ride.

 

Air Bags are a good idea, they will help the sagging problem you have, (with any truck), they can hold up to 5000lbs capacity, if thats is still not enough then you can go with a timbren kit that can handle up to 8000lbs, i personally went with a timbren kit cause when I wasnt towing or hauling anything I did not lose my factory ride or have to worry about the bags ripping or worry about filling the bags everytime I wanted to tow something, i have the same truck as you different year tho, this was the kit i got i put it in and forgot about it!!!!! which was the best part.
GMRCK25S Timbren Kit 1999-2010 Silverado 2500HD Rear Timbren Springs | $199.63