You call a couple of friends with strong backs, offer them breakfast and some of the haul, and go dig them up!
We ended up with 11 separate lilacs, both purple and white, some of them over 12 feet high. I now have a hedge of mature lilacs along the back fence, something I thought was going to take YEARS! A couple of them are very nice specimen plants, and we planted them other places in the yard. I'm feeling very accomplished.
Tomorrow, if it's not raining, there's hostas to divide, and more things to plant.
(Cross posted to gardening)