Sorry it took so long to see this message...been busy for awhile.
I asked the same question a few weeks ago, and the Hitec 645MG servo was recommended. I have bought one and installed it, but I have not had a chance to run it as I need to clean my diffs. (As I said, I've been busy) Anyway, if you can afford it, Airtronics makes a high-torque serve (200 oz) but I can't remember the name. It sells for about $120. The Hitec is about $50 (give or take on both prices). Hope this helps.