Converter Question

Okay so I'm trying to determine what stall my converter is. I bought the car with the engine/transmission done and the paperwork doesn't show what it has. I read here once that if you are driving along at 10 mph and you stab the gas pedal whatever your rpm jumps up to is what it stalls at. I've tried that before and it seemed to stall at 1800 rpm but I believe stock it was around 2400 rpm. It's a 1971 Dodge Dart with a 340/727 combination. Today when I took it out it seemed to stall at 2400 rpm and spun the tires pretty good. Something it hasn't done before. Short of pulling the transmission is there a way to determine what I have?