Unfortunately that's not practical, since these mailings are unique each time they are done. They could happen every few months, or once or twice a year depending on the projects I'm working on (I'm an architect).
I did find an Avery template at iworkcommunity.com. I use the 5160 which I found here: http://www.iworkcommunity.com/content/avery-labels-address-book-merge
but if you do a search of Avery Labels you can find most of the others you need. This works for what I'm trying to do as I had to type in all the addresses fresh each time anyway.
Merging with address book doesn't work well as it repeats one contact for all the labels on each page, so you get a page of labels for John Doe, a page of labels for Janet Scofield, a page of labels for Mom, etc. Not very useful for mailings.