If the head is genuinely 'brand new' I'd like to know who cast it and where. As for price, buying a scruffy 'unknown' ally head for a few hundred pounds (recent ebay prices have been in this region) and then having to find a further few hundred for machining (for those of us without extensive machine shop facilities), new guides etc. quickly approaches the £750 starting figure. Buying 'unseen' would be my biggest concern - and I note the 'no returns' statement.
I wonder if it's cast with -1549, ready to be overstamped with -1571. Have I remembered those numbers right?
If anyone has a large valve head going spare I'm interested!
T.