there are many different makes of real steel M14 stocks. The best candidate for conversion to an airsoft stock would be a "big red birch". Birch because it's stronger than walnut, "big red" are M14 stocks that have a beefier grip area than standard M14 stocks.
A guy I know who did his (Blastyman on that AirsoftPlayers.com thread) based it on a Big Red Birch stock. Time will tell how it holds up.
Of relevance is that G&G are planning to sell a Walnut wood stock for the G&G M14 for $100. Would seem to be much easier, albeit more expensive, to convert a G&G wood stock to a