Oh, forgot to mention a second option. It likely won't be as cheap as Greyhound, but you can at least research it.
Get yourself a pallet, just the right size for the boxes (slightly larger), stack the two boxes, and strap them to the pallet. You can them ship the pallet that way. I Googled freight pricing, and I believe this was the site which I used:
http://www.freightavenue.com/default.aspx
You can go there and at least get quotes on the pricing with the to/from zip codes and weight. Definitely specify that the pallet is non-stackable. It costs a little more, but you don't have a choice.
The freight class tends to be confusing, and I pissed off a shipper once when specifying the wrong one (I didn't know better).
Worth a try...
BTW, are those dimensions correct? 120" seems a bit long, unless that was a centimeter measurement. Actually, I'm gonna guess that's the case.