There are three basic Ford 10" converter "cores". The early Falcon 2 speed is the "tight" core and the Pinto and '72-73 351CJ s are considered "loose" because of the fin angles in the pump and turbine. The Falcon is (on average) 500 rpm less stall than the Pinto and 351C ( in modified condition). A loose 12" will (IMHO) be just as soft as the 10" you already have. The Falcon is easy to spot as it often has a ring gear welded to it and the "dents" for the internal fins are less angle than the other two. "I" recommend the falcon core for a tighter 10" OR an 11" ( C4 sourced) . The smaller the converter , the more "natural" stall you will have and the more torque you have , the more stall you will have. "Stall" is merely fluid "confusion" inside the converter before it goes into "fluid lock". Changing internal fin angles and cutting the stator blades increases the "confusion" and gives more "stall". Experience and testing give the converter builder the insight he needs to give you what you need/want. Some are better than others ( to say the least)
Randy
