rear end squat

I have a 2000 Silverado with 2WD and the 5.3 with factory tow package, auto transmission, but not the heavy duty suspension. I've had the driveline checked and it's okay.
I'm about to tow my boat and trailer (3800 pounds combined) to Florida from Minnesota with my 500 pound motorcycle in the box. The backend squats some but I should still be well below my towing limits. The Bilstein shocks have about 25,000 miles on them.
I've been looking at that various air lift products available to provide more support to the rearend. They may be the solution but I don't want to do anything half-assed.
Anyone have experience with these things?

If all your using it for is to tow a boat and trailer, and haul some "light" loads from time to time I wouldn't worry about the airlift bags. You could get air shocks, but I had them on my truck and hated them.

I'd recommend looking at getting your springs re-arched, as well as maybe adding a leaf. Or getting some heavier duty springs.

You should also replace your shocks, that could be your biggest culprit. But Bilstein's are excellent shocks.

Try balancing the boat trailer to get the tongue weight down to about 100-150 pounds. All you need is enough tongue weight to keep the coupler on the ball when you accelerate.

Get a weight distributing hitch.