The 340 is finally being rebuilt
Received this yesterday from Campbell Enterprises (http://www.campbellenterprises.com/jw_performance_wheel_sfi_flexplate.htm) for the Dart. When I opened the new Torque Converter from Performance Torque Converters (http://www.ptcrace.com/) the directions indicated I should be using a heavy duty flex plate with the converter. Did some Internet searching and came up with this one from Campbell Ent.
Here's some shots of the new one (round and beefy) and the original one. Looks like everything lines up properly, as far as the mounting holes, so we should be okay. With the 340 putting out >380 HP @ the crank, this seemed to be the right way to go.