Torque Converters??

Low stall was around 1200-1400. If you don't have a huge cam in your 408 it'll make it stall a lot more than that. Not sure what to guess but 72 340 is probably close.

Flash stall is what the engine rpm "flashes" to when you nail the pedal at a low speed in high gear. Many things affect what a converter will flash to such as engine power, weight of car, gear ratio, traction