Multiple Domain, Shared Database, Shared and Separate content

[mister]

Here's what I need to do .. let me know if there is any hack out there to accomplish it (and yes, I have vBulletin licenses for each domain).

1) Multiple Domains, Different Style (I found DDDS Hack .. looks like it would work)
2) Shared Users
3) Shared Content (a sub-set of forums appearing on both sites)
4) Unique Content (a sub-set of forums appearing on one or the other site)

#3 and #4 are the criteria that I need help finding a hack for -- #1 and #2 have been covered in other hacks.

Does this exist, or am I going to be busy writing a plugin?

Thanks for any info you guys may have