I have the Yank SS3600. I'm pretty happy with it. They are more expensive than the other guys though, by few hun's. the more extreme you go, the more they cost. mine was close to a grand. A more mild converter can be had for $300-500.

Its a pretty serious 9 inch converter, and drives nothing like stock. If you want a stock like converter, stick to an 11 inch. An 11 inch 2600-3000 stall would drive pretty close to stock.