Re: stall or no stall??
If you want to run the 4.11's then I'd suggest you'll need power from 3000-6500+ or they'll actually hurt your performance (I can vouch for this first hand).
Have you had the engine dynoed? If your making your power between 3000 and 6000, but not higher, then its probably best to aim for a 3.7:1 and run the 3000 stall. If your making good torque below 3000 i'd stick with the 1800 converter and go for a 3.3 - 3.5:1 ratio... that way you'll get to enjoy your engine's torque.
Just like a Tsunami.