So... What did I buy?

The - with a number after is for any change that is associated with that mold .
Certain cores will get damaged or wear excessively and those get a replacement core or section inside the mold .
Or it can be from a revision level change for the mold .
They discovered that there were having failures or difficulties in the process.
So engineers redesigned a mold or core and that lets them know if it was effective,,,,,or months down the road when they are having warranty work,,,they know what that casting came from.
I remember years ago I bought two 440 ‘s from a guy,,,they were 68 models he had pulled from a pair of old cars he had .
These blocks were cast 6 months apart but were assembled only 2 weeks apart by the 10,000 day calendar,,,,1 was cast in March 67 , and the other was Sept 67,,,,both had 10-67 bearings in them
The cylinder heads were immaculate and the outside,,,crisp lines from the molds ,,,the blocks too .
I’m assuming because they were from new molds,,,,looked great !

Tommy