Possible it was from a T400 but, it does not ring a bell so to speak. Number 42 on it could lead me in right direction but no one yet has stepped up.. Just picked up a copy of Colvin's Corvette by the Numbers 1955 - 1982 and on pg. 114, the imprint of the crank flange on the flex plate looks an awful lot like the 327 flange for 1962 - 1967.
Guess we gonna have to wait for Mr. John Z to help . . .