Recommendation Wanted: High torque rear end gears

I am looking for a reccomendation on a ring and pinion set for a non-automotive application from someone who has worked with a bunch of these. I am using it to orient a solar tracker with the sun. The ring gear would turn less than one revolution a day, forward and then backward but it could be under extreme torque (~2000ft/lbs). It needs to be very reliable and the more gear reduction the better. I would like something that is readily available and a reasonable price. I was thinking maybe something from a larger truck or performance vehicle. Any thoughts. Thanks and sorry for the non-automotive type question.

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