I've hauled around many V8 car engines in the back of my truck.
Believe it or not, I find setting them on an old tire (no rim) the easiest solution short of having a custom cradle
. Usually, I just use a 16" light truck tire. The tire bends and folds in all the right spots, supports the engine
well and has enough friction that it doesn't slide around the bed
of the truck too easily.
For extra security
you could use 4 ratchet straps to corners, but I've rarely found it necessary for short road trips.