I tried to ship a Miata hardtop greyhound; they wouldn't take it because it is too big and wont fit in their luggage compartment. (This is what they told me locally. But you may have better luck.) Oh greyhound is the cheapest shipper around period; but you do have to go pick it up at the bus depot.
I ended up driving the Miata with the hard top to a halfway meeting point with the buyer. All went well.

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"Our Lady of Blessed Acceleration...
don't Fail Us Now"