How about just a magnetic oil drain plug that collects the metal particles literally at the lowest part of the oil case where these shavings settle? These drain plugs from Fram are pretty cheap. I don't know how expensive filter mags are?
Ahh, whew... I was about to say, something placed over the air filter would be pointless.
I'd think a magnet over the filter, assuming it stays put, would help trap smaller particles of metal, though anything so small the filter cant pick it up is probably next to harmless anyhow. (Or non-magnetic.)
When I BBQ'd a rod bearing in my 420hp Honda motor a few months ago, after pulling the pan off, 98% of the material was non magnetic and the 2% that was magnetic was stuck to my magnetic drain plug. Personaly, you can get the magnetic drain plugs for under $5 at most auto parts stores (if the LS1 doesnt come with one stock, i've heard it does in some vehicles) and it does work so long as you wipe anything off of it after each oil change. Basicly, a great majority of the "wear" components in the engine are non-magnetic. (Bearings, aluminum parts, etc)