Please post the stamped serial number on the machined pad behind the distributor. That's going to be more useful than the casting numbers, as it will usually identify not only the general age of the block, but the specific application and year of the vehicle it was installed in originally. The block casting number is also helpful- - - -down near the oil pan rail near the fuel pump hole.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!