Here is a list of ELC's that would work:
CAT HD ELC
Fleetrite HD ELC (International's brand)
Rotella HD ELC
Prestone HD ELC
Zerex Extreme HD ELC
The latest formulation of the Delo ELC has a maintenance-free change interval of 750K miles/8 years or 1M miles with an extender.
Chevron DELO ELC is the bomb!
Fleetrite / Rotella ELC : The Rotella is the same exact stuff as the Fleetrite, just in different bottles and it's the best type of coolant to use. Just make sure you do a proper flush and use distilled water.
Zerez Extreme Duty (RED)...you can get it at Napa. It is already pre charged and doesn't require any monitoring or additives.
FYI, there are two types of SCA. DCA-2 and DCA-4.
NapaKool is a DCA-2 SCA.
DCA-2 is a Nitrite-only based SCA. Nitrite is the primary and most effective cavitation inhibitor in any SCA. DCA-2 usually contains potassium buffers, free of phosphate.
DCA-2 was the first SCA, and it remains the most popular. It can be tested with any test strip that shows Nitrite levels, either a 2-way or 3-way strip.
DCA-4 is a Molybdate/Nitrite based SCA. It uses both Molybdate and Nitrite "synergy" as a cavitation inhibitor. DCA-4 usually has sodium buffers and phosphates.
DCA-4 is somewhat harder to find, maintain, and optimize. It can be tested with a 3-way test strip, although conversions are available for using 2-way strips.