acceptable substitute battery
My advice: Use a BCI group 24 battery w/a CCA of around 650. I know that is less than a CCA rating on a 6TL. But in your situation, who cares?? The starter on your truck only pulls 950 amps at maximum resistance(which is measured at 0 degrees F. at 10 seconds load). May I suggest a reputable battery such as Deka, ACDelco, etc. Avoid Retailer brands as they use recycled acid that does not maintain the specific gravity necessary for periods of storage. In effect, they will discharge at a faster rate than a premium battery whicj uses virgin acid. You should be able to purchase (2) UL 24 Deka batteries for about $150.00 . The warranty should be 84 months total. The first 36 months is free replacement, with the warranty being prorated after that. Jeff Hill, Manager of Fisher Auto Parts, Lewisburg, WV 24901
P.S. Deka batteries have been used by state/federal gov't agencies for years
because of their value. They have been used by the state of WV gov't agencies AT LEAST since my Dad went to work for them in 1984. They are a great battery....