It'd be great to grab a head in top condition with the milled underside.

Maybe some pictures would help sell?

If all else fails, try ebay. You might be pleasantly surprised.

I start all my auctions at $0.99 and offer cheap or free postage. This tends to get the punters interested much earlier on.

I would be weary of making ALL your money back on your A12 head though, if it still had the springs you'd have a standing chance of selling it for at least half what you paid for the work.