The GM tablets have settled into the combustion leak in my 93 6.5. includes the 99 on up to the 580 over altamont pass. Gauge to the left of the middle like the old days. Next test the grapevine.
I just bought several 20/50 qts marked down as adders. Still pretty clean. Added one pack of tablets to rad. Ground tumeric, ginger, almond shells.... Used in my meatloaf too.
I put two coolers on mine and the fluid stays red a very long time. Same guys do it and they always take something I have in the back that I picked up at the marina for free. Water skis, outboard, etc.
No thermostat in the summer slows the get hot from the combustion leak. You got the whole rad to cool with from the begining. A quick 190° then the leak pushes it up from there fast. At the grape vine I through buckets of water through the rad until the temp drops way down and then proceed slow...