Hi Roger,
Wow, you almost don't need my help at all! Here's what I can confirm/add to the discussion:
1a. You can order any fingerboard dimensions by specifying the width at the nut and the last fret you can measure (please specify if it isn't the 24th fret). On a Mark King model there is no additional charge for this service. Likewise we can carve the neck any way you like, but that is much harder to describe remotely. As sugested, you can send us a bass you like the neck on and we will duplicate the feel.
1b. We'll scale the artwork to fit the fingerboard size on your bass. Since the inlay work is done completely by hand, it won't be a problem.
2. If you've got a specific brand or gauge of string you want used, just send me a set and we'll make the bass to suit those strings. This is especially important in England where it seems 45s are considered heavy gauges. Enlarging the slots is easily done by a professional, but if you want the strings much smaller than originally supplied, you'll need a new nut, new saddles, and a professional setup.
Without instructions otherwise, we set up with very low action, then raise it so most players can use it. We want to know it will play low, as raising is simple if you've undershot it.
3. The 4-string Mark King averages just shy of 15 - of course it does depend on the neck width.
4. As reported above, the fingerboards are left unfinished, including the sides. Bronze, silver and aluminum all will tarnish some. The aluminum tarnishes the least and will usually not show becuase even casually wiping with your finger removes it. If the silver or bronze dots get very tarnished, a light sanding along the edge will expose a fresh untarnished surface. Hey - LEDs won't tarnish at all.