The 2500 Suburban was the original 3/4 SUV, older models had the 350/454 motor options with TH400 trans, 01-06 they were available with 6.0/8.1 and 4L80E trans, 07-13, only had the 6.0L but with the 6 speed 6L90E trans that kept the tow ratings the same. Ford made the Excursion from 00-05 available with the 5.4, 6.8 V-10, or 7.3 diesel.
Back to your current situation, the first thing you need to do is get to a Cat scale and see what your weights are. Expy's have coil springs for a soft ride, not the best for stabilizing a load. I towed with one for a year before trading it in for a 2500 Suburban. I added airbags, and they helped a lot, what I did wrong was connect them to a common air line, so they didn't help with body roll, just sent air from one bag to the other. If you add them, plumb them separately.
Also the transmission in the Expy is not very sturdy, be sure to add a trans temp gauge andd possible an aux cooler if you tow with it on the regular.
