727 take off problem

Well it does sound like you have a high stall converter. Take it out on a back road, come to a complete stop, nail it. Look at the RPM gauge right when the car launches and that will tell you the flash point of the converter once you start to move. It sounds like a rather large stall than what you need but I don't know all the facts about the car.

If you just start off at a red light and the engine revs pretty high before the car moves that is for sure a high stall converter. Make sure a trans cooler is installed because the stall produces more heat.