Good question!

I went looking about and found this site that pretty much told me nothing.
There is a lot (massive) of part numbers in English and Swedish. Let alone a method code.
http://www.volvotips.com/parts-catalog/240/Volvo-240-260-1985-1987-parts-catalog.pdf

It uses chassis numbers for the most part.
Around page 30 it shows the stamping points on 4 & 6 cylinder engines.

There is another section with the type of engine B230 A - F with .XX for years made for each letter.
Came up with no clue where the .xx number gets reused.

As far as the year on the engine blocks, I can only imagine it will not be there. No layman system shall relate to a decipher or year correlation.

There are reasons for this!
Number one reason is...No one wants to know they got the some last years engine in their NEW car!

First of all the blocks are made in large batch runs or pours of metal. Tracked in quality control inspections and then stored for a period of time. This may cross a year or more of model years before seeing any machining process.
At this time they are only tagged without stamping.

In my day they call it a "seasoning period" for the iron, which might be a bunch of malarkey, to let the iron crystals release internal stresses.
Harley Davidison and the British bike companies let them set 6 months or more to chill or stabilize on shelves. The claim was the cylinders bores produce a finer grain structure surface and therefore a smoother finish.
When I was a kid I hung out in a small motorcycle shop and observed cylinder boring done.
The chips varied in feel and color with different brand bikes. We did Honda, Yamaha, Italian Gilera's, Ducati's. BSA's and Triumph's with Harley's.
Of those, the Brits cylinders looked and felt the best, straight off the boring bar. Better metallurgy I think was the reason and maybe seasoning, who knows?

Anyway back to numbers. The castings are brought forth under production orders and blueprint revisions. It is then numbers are assigned when the area gets cut flat.

The production number should be sequenced number, possibly tagged to a revision number by recording the break number only and the production continues on the same way until another break number recorded. This works for in-house manufacturing controls.
Sales, VIN and literature departments can have and used the information.
The year number, actually in the number, is irrelevant.

You can back track these numbers by working with those numbers if you know the number of cars produced in a calendar year. You take some engine numbers in one year to the next and add or subtract the production to come up with a spreadsheet. I would say you need at least a three year or more year spread to be accurate to within a few cars of what is where.

Now I can suggest that you got to a state registration inspection station. Ask their vehicle inspector, you might have to kiss up to him, to look up the number. You give him a good enough reason he should help you. Nowadays, it could be a minor fee involved.

It's my belief they have all kinds of information on numbers, tags and some hidden plates not in any normal manual! They are fraud and thief bureau books.
He won't share anything else. If you have a good number he can determine where that number broke into what year. You will never see those books!

Good luck and let us know what you find out!
Phil