balanced flex plate on balanced 360 cid

The hard thing about contacting the builder is the motor was built 12 years ago and has been put up .Thanks for the external,internal explannation guys this makes understanding and reminds me of what was forgotten.When I was racing I ran both 340"s and 360"s . I am the one who put the flex plate on ,this was a manual engine and I hooked it to a auto . That is why I asked about flex plate cause it was me that made the change . My builder is long since gone from the area but if I ever do bump into him the questions will fly. I still have bodywork to finish so not running car until I change flex plate is easy. Just finding time is the problem.
thanks
R BEE
you can check out car at my 73 restoration by R BEE there is a sound clip on page 2.