I have an older (2002-era) Win Mod. 70 Black Shadow. Barrel contour looks to be about a #3. I'd like to pick up a factory wood stock for it but was wondering if the featherweight stock would need to be sanded down to fit the barrel? And, if sanded, would it be too flimsy and/or thin to use off of sticks/bi-pod/sand bags?

It depends on the FWT stock you buy. If you buy the FWT stock that is inlet for the magnum cartridges your barreled action should be close to a drop in fit. The M70 FWT magnum rifle use the standard sporter contour and not the same contour as the standard .30-06 or .270 FWT rifles.

I agree with what Taylorce1 said and to add to it even if you had to open the barrel channel a bit the Featherweight stock is not flimsy or flexible.
Try CDNN they usually have Winchester factory stocks in their inventory.

Thanks. I was looking at the one's on CDNN. I just wanted to be sure I didn't end up with a splinter fore end after sanding out the channel.

If I understand you right, you're going to try to sand a stock barrel channel out to fit a larger barrel? That's hard to do and make it come out even close to fitting, and even harder to make it come out looking good AND fitting right.

The normal procedure is to use chisels and scrapers to re-inlet the stock to fit the larger barrel. Much more precise and ultimately, better way to open up the barrel channel. Not too terribly hard to do, but the technique needs to be right to get good results.

You might do a google search for inletting a rifle barrel and see how it's done properly. You'll be a lot more likely to get good results if you approach it that way.

And on the other side could one take a standard sporter barrel and refit a featherweight stock to work or would the balance be all off?