What about the Keisler 4L60E kit? Does it require cutting? I don't see what the price is on that but I would bet a similar $2800 to the GV. The GV at least has the ability to split all the gears making a 6 speed auto, not just adding overdrive.
Oh... I just looked at some of the Keisler info, needs major cutting, hit and miss quality, and is more like almost $4000 by the time you get everything for the most basic transmission. GV definately beats that.