Will a New Haven M70 LH Classic in 30 06 with its factory bottom metal fit into a Featherweight stock? In other words, same bottom metal?

Yes if both are the newer one piece or if both are the older two piece floorplates. The barrel channel of course will need opening up to accommodate the heavier barrel. I assume the "classic" is a sporter contour?

correct. Thanks. If it turns out the older is the two piece and the stock is for one piece can a one piece bottom metal unit be found?

I believe it can but I'm not sure. Perhaps someone with a bit more experience smithing M70's will chime in.

PT&G makes a one piece bottom metal. They dropped in on my stocks.