Is there a list of which kernel version comes in each Android AOSP version?
Or lets say, which version /proc/version would spit out.
You can find all of the stock kernel versions at the Wikipedia Android version history page. It has the kernel version for each version of Android; it's at the end of the descriptions of each Android version.
Table from Wikipedia:
Note: other “distributions” of Android might run different kernel versions.
Anyone is welcome to correct and expand this table. Please keep formatting.