The 2 Sierra's I used as daily drivers both had the 4.8, they actually weren't terrible on gas, considering they were a truck. A 5.3 in a regular cab short box is almost impossible to find. I daily my Lightning too, what's gas mileage?
. My commute however is pretty short, so that's probably a big factor.
I hear ya though man. I loved both my Sierra's as dailys, never really had any problems with them, both were pretty solid trucks. That truck would be a good daily as well, I think you would be happy with it. Is it the work truck package (no options, probably a rubber floor), or does it have power options with it? Lots of aftermarket stuff for those too if you end up going that route down the line. A 4/6 drop on them look perfect IMO.
The thing I love about regular cab short box's is they are really roomy on the inside, since they are full size trucks, but are still pretty easy to drive around, park, etc, since they aren't too long. I will however say that going grocery shopping in them is a bit of a pain, we take my fiance's car instead since there's no where to really put the groceries if you buy a lot