said by timcuth:How do I go about doing this?
While it is not an exact science (as Cabal
correctly states there is no requirement for IPv6 assignments to be related to prior IPv4 assignments), what you can do is looking up ownership and possibly associated AS numbers for a given IPv4 block by contacting the relevant IP number registry (www.arin.net for North America).
You can then check the IPv6 address assignments to the same owner. There is a high probability that any dual-stack servers (those with both IPv4 and IPv6 addresses) can be found within those IPv6 blocks.
You didn't explain why you have filter rules for those specific address blocks (and perhaps you chose them for illustration only) but there may be other addresses you may have to filter in addition to any new IPv6 addresses that may get assigned to those blocks.
Depending on your exact scenarios and security needs you may also have to block IPv6 addresses that embed those IPv4 address in various address translation and IPv4 to IPv6 transition schemas (e.g. Teredo, 6to4).