There are only a couple things that a torque converter can do -- stall at the stock RPM, stall at a lower RPM, or stall at a higher RPM.
We all know what the stock stall speed feels like, so what happens if it stalls lower or higher?
Well, lower would have it "creeping" while at idle, requiring firmer brake pedal effort to stand still when stopped in gear (and that's all -- once it is engaged, there is no more difference in performance).
A higher stall RPM would mean that under load, the converter would continue to slip unto the set RPM was reached, and the truck would not move until then (and again, that's all -- once it is engaged, it is the same as any other converter).
So, unless you are wanting to play with your launch speeds under load (such as a drag race start, where the brakes are held via line-lock until that last yellow light) you are probably best with the stock stall converter. Going lower only heats everything up.
Now, if your converter is stalling at 2000 RPM under load, it is likely either the wrong converter for the application (swapped in from a smaller motor setup, which the higher torque of the bigger engine can over-stall) or it is a purpose-built high-stall converter.
As far as the 4.56 gears being the right choice for your setup, I'd say that they are -- they are as close to stock ratio as possible. If you wanted a performance advantage, you should have chose 4.88 or 5.13. As I recall, from the conversation about your gears, you were worried about going as high as 4.56. I also recall that we said it wouldn't be that big a difference... Guess it wasn't.
