The engine numbers are found on top of the block near alternator plate. See above the overview of the suffix for each year.
Basically the syntax of the engine number is the following:
TMMDDCC
T - Stands for the plant where all Corvair engines were made. Tonawanda, New York
MM - Reflects the months when the engine was produced
DD - Refflect the day when the engine was produced
For example the engine code T1008YR is from an turbocharged engine build on the 8th day of october