I'd stick to the regular longrifle-stock-blank-supplier food chain, unless I really knew my wood. They will know what dimensions you need for a given bbl length and will sell you suitable wood for a gunstock. Other sources may have pretty wood that could be unsuitable for a gunstock for any number of reasons-they might be quite ignorant (no fault of theirs) of what exactly makes a proper gunstock blank.
Really hard to comprehend how much wood we need to begin with in order to find the pretty little stocks contained within.
Having two blanks handy on hand right here, I'll measure them for the record.
Blanks (in general gunstock shape):
Curly Ash from the Harrisons: 62.5 x 10* x 2.25" - 11lbs
Walnut from Jim Kibler: 64 x 9* x 2.375" - 12.5 lbs
A finished stock weighs what? a couple-three pounds at most?
*Also note that the middle figure represents how wide the blank would be from end to end if rectangular. The butt is not that wide, there is drop in the shape of the blank.
Green wood will be thicker and heavier of course.
Oh and also, I "messed up" my first stock somewhat, but decided to live with it. I mean i fixed a lot of errors (that's learnin') but another 1/4 inch of this particular error would have trashed the whole piece (short of a large patch). As it is, it will always bear saw tooth marks on one side, and be a bit "unsymmetrical" left to right. BUT then i spent half as much on that wood as I did these (samples above)...pretty wood is such a temptress!!!