The 3 rib is stronger so I have been told, mine is out of a Z06 and it's a 3 rib. As for the stall a lot of people say a higher stall seems sluggish for normal driving but I think that was in the older days of the hole shots and such, todays converters are a lot tighter. I have a 3200 Vigilante and as far as I'm concerned it drives like a normal car until you mash the gas and then it's like a slingshot.
It's not a great method but you could try pumping up the brakes and then hold them as you start to give it gas, the tires should start to spin around the stall RPM but you will probbaly blow through the brakes before that happens and that's why it's not a great method.
I hear tell that you could also coast along around 15 MPH and then floor it, watch the tach and when the car takes off that is around your stall.
Best way would be having a data logger that you could actually go back and read data from a launch.
Maybe someone else has a better idea.
