Yes, I ran a Odyssey PC680 in my Mustang drag car for about five years. It's a 680 CCA battery that weighs 15.5 lbs including the aluminum mount I TIG'ed up for it. There's no real advantage to saving weight on a tractor though. /forums/images/graemlins/smile.gif
I found it worked very well when the car was used regularly, say once every couple weeks or so. If it sat for a month or more though, it would run itself dead. I bought mine through batterymart.com, I think it was $70 when I bought it. Compared to the brand name "Dynabat" which is available through Summit Racing, etc, that $70 was cheap. Dynabat's are just re-badged Hawker Odyssey's for twice the price.
Also, if you order the part numbers with the "MJ" at the end, it comes with a metal casing bonded to the outside of the plastic surrounding the cells. Makes for a very tough battery.