Having built more than a few AOD's, I can tell you two things right away. Your C6 does in fact use a 164 tooth 28 oz. flexplate. The AOD also uses a 164 tooth 28 oz. flexplate when used behind a 351W. It is NOT the same plate, however. ABSOLUTELY DO NOT try to use your existing C6 plate with an AOD. The depth of the plate is different and you'll destroy the transmission and possibly the thrust bearing in the engine as soon as you start it up. There is a 164 tooth plate available with a 28 oz. imbalance that is specifically for AOD and C4 applications. That's the one you want.
The second thing is do NOT mess with ANY AOD built before 1989. There were critical lube system and valve body improvements made in '88 and '89. Earlier units will lose their cookies all over the highway in a short time behind a healthy 351.