Related to this thread, I was looking through a local hardwood place that sells mostly dimensioned lumber, and found a couple of lengths of black walnut that are entirely sapwood. They are each about 3.5' long 1x4s, so dimensioned down to 3/4"x3.5". They were at least double my usual bdft price for raw lumber, but entirely sapwood in that size was worth it.

Pale binding perhaps? Or blocks for inlays?
Just due to the time frame waiting until we start, I have a feeling I'm going to overthink this build...
Edit: I also forgot to mention that one of my favourite nearby suppliers carries quartersawn black walnut fingerboards - but only has them listed in guitar widths/lengths, so I sent them an email asking about the dimensions I'd like to see. Worst case scenario, I could make my own fingerboard, sigh...