Cynthia disappeared from Oakdale, NY not from OaklandThe only one that imo, till now, could be the girl (how far fetched) is Debbie Lee Shelton; murdered in 1969. Only 12 but older looking. And from CA, while Alcala was in NYC. Her face is very similar even though our girl seems to be chubbier.
Ps, equally likely imo is Cynthia Dawn Constantine. Disappeared in 1969, but in Oakland N.Y.
Debbie Lee Shelton 1969