Ship it via FedEx ground. It will be the cheapest. Bare blocks are cheap. Obviously the heavier the more expensive, but just make sure to box it nicely. I typically use a fiber board box from a moving company. Tell them you need a used one and they typically will give it to you. I usually wrap the block in some solid 3-5mil trash bags and tape it up. Then spray expanding foam in the bottom of the box. Let it expand a little then set the block in it. Then spray the rest. The fiberboard boxes have like 400# weight ratings so no need for anything other than the foam. Just make sure the bag is taped up sealed and it doesn't wiggle in the box. I have drop transmissions packed this way off the back of a tailgate on a truck with no issues. I have shipped probably 50 blocks and motors this way over the years.

BTW, whats up with the motor?