Join Date: Sep 2011
Location: The Hill Country of Central Texas
The casting code simply means that the part in question was designed for the model year indicated. That design may have been used for many years. You need to find the date codes that are also cast into engine parts like the block, heads, manifolds, etc. These will tell you the exact month, day and year the part was cast on. If your car was assembled in August, 1968 the engine date codes should look like this- 8F30 or 8G6 which represent 1968 June 30 and 1968 July 6 respectively.
According to Federal Law the manufacturers were supposed to start stamping a portion of the VIN into the engine block for the 1968 year model but there are many known examples where it wasn't done.