Sorry if this is a lame question. I'm considering buying a headless bass and putting the parts (neck, pickups and bridge/tuners) on a lefty body. How do I know how deep to route the bridge/tuner assembly? Sorry if this seems dumb but I have no clue. Thanks.
Route the cavity for the bridge/tuner so that when you have a long ruler on top of the frets you have the ruler touching bridge saddle pieces. This way you have all the string height adjustment usable.
MpU is right, but I would add that the bridge saddles should be bottomed out so you can raise the strings up from top of fret height.