When I sent my 2 cores, I used Uship.com.
This girl who lived up that way, does it for a living going back and forth from L.A. to Washington hauling stuff.
She had puppies and some furniture to deliver too.
I put the steering box in a milk crate, sealed up and it was like 50 bucks for 2 cores sent.
Uship.com is pretty good. They don't get paid unless it gets delivered.
They do rely on good feedback so they can earn other future business as well.