I can see the "CON 4" but the remaining is too blurry to read. The "CON 4" indicates the assembly plant conveyor number the engine was assembled on. The other would be a single letter (that corresponds to the month of build), followed by 2 or 3 numbers which indicates the day of the month and year built.
Of more importance is the stamped serial number that you should find on the flat machined pad directly behind the distributor mounting into the block.* That set of letters/numbers will give details on the engine model year and original vehicle it was installed in. That's where you will have the best info for confirming if the engine was originally equipped with mechanical or hydraulic lifters.
* If there is not a stamped engine serial number, it's probable the engine is a service replacement.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
