The BB is a usually a good starting point for a timing setting but, for many reasons, it is unreliable as the final ignition-timing setting.
The vacuum gauge is the cheapest, easiest, and most consistently reliable way to adjust timing and carburetor mixture (and to get a quick/easy look at the overall condition of your engine). If you keep an eye on Harbor Freight sales, it is nice to have a vacuum gauge in your garage and in your truck.
