Block Casting date vs Body build date

[gzig5]

What is the general approximate time lag between when a block was cast and that engine going into the car?  I always hear about "date coded" engines that aren't numbers matching.  I'm not a big numbers person, but I am curious.  My restoration will not be to original condition.  Original motor/trans long gone, but I have an extra 340 block that might be a decent date code match.

Casting date on the motor is 5-24-72 (from memory) and the sticker in the door jamb says 1-73.  So about a six month lag between the block and car build.  I have the build sheet but it's not accessible at the moment. I know it isn't THE motor, but could the original have been from May or would it be later in the year, closer to build date?

[anlauto]

The block should have stamped numbers on the front of it that will tell you the date of the assembly of the engine. If the date is prior to the assembly date of your car.... 0-90 days before is a good window to make the claim of a "date coded" motor. This is all just a matter of opinion...

[gzig5]

Thanks.  I forgot about the date stamped on the front.  Mine is very poorly stamped and is only about 50% legible but best I can tell gives me a mid-Sept 72 or early Oct assembly date.  That would almost allow me to lay claim to "date coded block" when my heirs go to sell it, after they pry my cold, dead fingers from the pistol grip.  

I've got the broadcast sheet and am trying to figure out if i can narrow the build date down from that.