Many rod makers, including me, use the Dale Clemens formula available on the web site Bajema posted. The web site also has a calculator by Wayne Cattanach, the guy who taught me rod making, that does basically the same thing with different parameters. Of the two, I find the Clemens formula easier to understand.
Use this as a starting point by taping the guides on. Run a fly line through the guides, bend the rod, and check to make sure there aren't any big (or small) gaps between the line and the rod. If there are, adjust the guide placement or consider adding an additional guide and recalculating. This process takes the taper and bending profile of the rod into account. It's especially important to do this on a long rod like yours.
Once you have the guides positioned the way you want them, go out in the yard and make a few casts to make sure the line flows properly. If it does, and the rod casts well, it will motivate you to get the rod finished!
I have spacing for the ARE 3pc 11ft 6/7wt. It should be pretty close, but I would tape the guides on an static test them. Send me a pm and I can send you a link to a Dropbox folder That I have saved a bunch of rod building resources.