Just for fun I put a cylinder head shipment into the USPS web site to see what they would charge.  I made the box 24" X 6" X 8", weight of 30 pounds, value of $600, to correspond with one cylinder head.  The price they quote was US$138.10, with delivery in 3-5 business days.  Normal USPS Parcel Post may be a little cheaper, but not much.  
Anybody here in the US ought to be able to ship a package that way; that is how I'll be shipping my intake adapter when they go internationally.  By the way, an intake adapter to the UK would cost exactly the same price.