Keep in mind that block ice is rather large and may damage your fish during transport. Small cubed ice would be much better.
Seems like the block ice lasts longer tho, but Ice is Ice and melts at 32F. 10 lbs of block ice has the same BTU's as 10 lbs of crushed ice or 10 lbs of cubed. I don't think I would use those contained ice freezer gizmos because it is a contained mass that could easily bounce around in the tank and damage the fish. Raw Ice, and let it melt on the trip.
Good point from Cecil on the source of the ice too. If it's derived from a municipal system, could be the nail in the coffin on the next haul.
Mind your P's and Q's, and don't get all OCD about it. Take it easy
