Quick update, I found a .cal file for a Corvette with an LS6. Jet DST can read a .cal, but I guess not write one, so I copied all the tables that were fuel injector related and put them on my 5.3's computer. It is no longer giving me a code saying that it is running lean! It sounds like it is running well.
Now I feel a bit more confident driving to an actual tuner whenever that may be.