Got to love good hardwood. Did your stock come with all the hardware, or is it just the wood?
EdwardE wrote:The natural color of the walnut is very different from the forearm so, it looks like I'll have to do some staining (which means re-working the forearm, too) to get them similar hues
Are you comparing the stock to the fore-end in it's current finished state, or to the fore-end before it was oiled? Wood can look very different between finishing stages, so the stock and fore-end may be better matched than you think. To help decide if you really need to get into fiddling with stains, you could sand a spot inside the fore-end to the same state as the the stock, and use that to compare the two.
EdwardE wrote:There's a little bit of figure in the grain; no show-stopper, though.
Police walnut stocks are meant to be tough and functional first. A good, straight grain structure makes for the strongest and toughest wood -
if the grain is oriented properly relative to how it is loaded. It's fairly easy to split wood along the grain, but extremely difficult to do so across the grain; something I learned very well spending the bulk of my tweens and teens in a wood stove-heated home.
This makes wood weak against bending perpendicular to the grain and shear forces parallel to the grain, but very resistant to everything else. A gun stock (on a properly engineered gun) only experiences bending about and shearing across the lateral and vertical axes. The stock isn't wide or tall enough to allow for much of a bending moment around the longitudinal axis, and with a proper bearing surface on the back of the receiver, the only axial load in the longitudinal axis is evenly-distributed compression, not shearing.
So, aligning the grain longitudinally plays perfectly to the strengths of quality straight-grained hardwood, making for a wonderfully durable stock. My old Police walnut stock has the grain perfectly oriented, parallel with the stock bolt and perpendicular to the bearing plate on the back of the receiver (the grain on yours isn't quite as optimal, but it's pretty close).

As an engineer, I find this to be the most attractive figure out there. Crotch, quilted, or burl figures may be showy and visually striking, and I love seeing beautifully-figured grain in decorative roles, but that fancy stuff will never beat the strength and toughness of a good straight-grained shotgun stock.