Since it has to go by truck... you also have to compute in the weight of pallet & packing. The trucking company should weigh it for billing purposes. My guess is 505 lbs total shipping weight.
I've shipped one engine ( a 400M complete) and it weighed in at 540 lbs with the crate. But the trucking companies round up to the next 100lb increment, making the weight on that 400 at 600 lbs. A 302 longblock will be at least a hundred lbs. lighter possibly two hundred.