I've owned and towed with both 1/2 and 3/4 ton Suburbans. I don't recommend a 1/2 ton but if you insist, start with air bags for the rear coil springs, a rear stabilizer bar, an auxiliary transmission cooler and a real transmission temp gauge, a quality brake controller, towing mirrors, heavier rated wheels/tires (preferably 10 ply), the best weight distributing hitch you can afford and possibly a heavier duty receiver. With all that being said a used 3/4 ton is really no more expensive than a similar 1/2 ton. Some of the same upgrades mentioned above may still need to be done to the 3/4 ton though, such as towing mirrors, brake controller etc. but you will get heavier axles and suspension, bigger brakes, beefier transmission and transfer case, bigger radiator etc etc. and the 3/4 ton will really get just as good of fuel mileage as your 5.3 towing.