If you have the right B&M flex plate for a 360 it is already externally balanced for the 360 (It will have a large notch taken out of about 1/4 of the diameter which removes the weight on that side for balancing) if it does not have the notch it is the wrong flexplate. nothing needs to be done to the torque converter or transmission. you need to contact TCI and confirm you have a 904 10"" convertor (which is correct). do you know the stall rpm of your converter? it should match the performance curve of your cam and the rear end size you are runnuing or it will not perform optimumly. you should contact TCI and find out the applications for the torque converter and contact B&M for the application of the flexplate. just give them the part numbers and they can tell you the applications. There is no need to guess as long as you know you have a 904 transmission (numbers are found on the case). make sure the flexplate is an externally balanced 360 and that the 10" converter is for a 904 (and what stall rpm). if they are both correct it should bolt up just fine, however if the stall rpm is too high or low for your engine it won't launch very well!!! Stall speed is the rpm that the converter has full grip. you can get an idea of this speed by putting the car in drive, holding your foot on the brake, and note the rpm (you'll have to have a tachometer) where the converter grabs and stalls the engine. The stall speed determines the "snap" you get when you launch the car drag racing. It's kinda like how you pop your clutch launching a manual transmission car. if you do not intend to race it, don't worry about it the car should still drive ok.