I've hauled several stovebolt engines hundreds of miles using a slightly modified version of the wooden cradle. Mine are made of 2X4 and 2X6 pressure treated lumber, and they support the engine along almost the full length of both oil pan rails. Those cradles are very stable, support the engine upright with no spillage, and only need a couple of ratchet straps to prevent tipping. I brought four engines back from last year's Homecoming on a 16 foot trailer that way, 700-something miles. I even had to make a couple of panic stops, thanks to idiot drivers.
Jerry