Question for you restoration guys and our purists?

[67 cst swb]

My 67 CST originally had a 327 engine stamp date (front pass cyl head surface) of V1220YH as determined in the protect-o-plate.
But, the original motor is gone.
Not that it hugely important but...
What would have likely been the casting date on that 327 block, in order for it to be stamped 12/20 (I'm assuming Dec 20th 1966 as my VIN code is J122461.)
Would the block likely have been cast in November sometime or December or could it have been as early as August of 1966 or ???

My thought here is:
I have to find a block/engine anyway... I might as well find something close to that approximate original cast date... as I still have the original trans and rear axle that match the protect-o-plate. It may be important to someone else someday.

And if you could help out with a possible block casting number, that would be great as well.

So if any of you guys with a original engine 1967 327 could shed some light on what you have, that might be helpful also.

Thanks