Use Uship:
http://www.uship.com/
Uship is sort of like the eBay of shipping. You say what you need shipped and where, and drivers bid on it. If you are patient, eventually someone who is going from where your load is to where it needs to be, and who has the space, will give you a good price.
You explain your situation, and you work one-on-one with the driver. For example, if someone is towing a trailer, you might just strap the engine to a pallet, tell the driver that you will help him to lift it into the bed of the pick-up, that there will be someone on the other end to help him unload it, and that you just want it covered with plastic and not sliding around. In this example, the engine would be gravy for the driver -- his real load is the trailer contents, so if he is going your way, you might get a great price.
From start to finish you are dealing with a single handler who understands what you are shipping and how it needs to be cared for. The drivers get feedback, just like on eBay, so they are very careful not to screw up.
I've had two motorcycles shipped this way. One was strapped in the bed of a pick-up that was towing a trailer, just like the example above. The other was strapped inside a cargo van, the van was empty, the driver was returning from delivering a load.