I am just throwing out there. Look for a GMT400 K2500 with the 7.4 in the burb flavor.
I purchased one after owning a FJ62 Land Cruiser and came to the realization that it wouldn't haul my wife, daughter (car seat), and the dog with camping gear. So I sold it and purchased a Suburban and have been using it.
I get in the teens for mileage, can tow up to 11,000 lbs and have space for days. I need to get better at how much gear we are bringing. Only advantage over the later GMT800 is cost. I really wanted to go with an 8.1L but I was able to pick mine up in Portland for $3k. I have had to do a fuel pump, fix the A/C and new tires. It has been a solid truck