I'm about to brew a Traditional Bock, a Doppelbock, and a Maibock.
From what I've read...a Doppelbock has a higher OG than a Trad Bock but it attenuates less so it only has a little bit more alcohol. Also; while both are very malty, a Trad Bock is a more toasty and a Doppelbock is sweeter/caramel-y.
I can't remember the exact number (I'm getting much of this from Daniel's Designing Great Beers) but a both have to have a minimum OG to be called a Bock or Doppelbock. I think it's 16 degrees Plato for a bock and 18 Plato for a Doppelbock. A Maibock is the same OG as a Trad Bock.
My recipes are mostly Munich malt as the base but also with some Pils (reverse that for the Maibock). I plan to use some Caramunich in both dark beers. Then Crystal 60L in the Doppelbock and Special B in the Bock. Then a tiny bit of Roasted Barely (more in the Doppel) in each of the dark ones to give them a deep color with lots of red.
I'm gonna use mostly Hallertau whole hops...all bittering....and not too much. Looking for malt dominance.
EDIT: So something like this:
Traditional Bock
83% brewhouse efficiency
6# Munich
6# Pils
.5# Caramunich
.25# Special B
.125# Roasted Barley (at most...maybe as little as .0625#)
2 oz. Hallertau 4.3% AA @ 60 min.
Should be in 1.072 neighborhood with ~25 IBU and 17-19 SRM.