Balancing cast crank 340

I hope you guys and gals can help me. I am rebuilding a 72 cast crank 340 in a numbers matching car. It is a late 72 model so it has a cast crank as the 73s do. I want to earlier 340 pistons to regain the compression that is lost in the 72 and 73 models. Does anyone know the correct weight piston for the cast crank motors, are they the same weight as the steel crank motor? I checked the weight of my used pistons to the weight of "replacement 340 10:1 pistons. My used pistons were 90 grams lighter (the motor was previously rebuilt with .040 pistons so I do not know if they are correct). I plan on balancing the rotating assy but would like keep from having any miss matched parts problem. Also the weight on the torque converter is not the same as a 360 is it? Any spec on the amount on weight that should be on the tc? I bought this car as a basket case. The trans had been replaced with a 904 that did not have any weight on the torque converter, surely the motor was vibrating. I know a 360 shakes bad without a weight on the torque converter. Any help or suggestions would be great, thanks Ray