I use wood 2x6 and or 2x8 nail together to fit the oil pan and notch them to clear the crankshaft on both ends to haul engines all the time BB don't need notching.
I do make the ends wider than the center pieces also for stability: wrench:
I put 3 to 6 inch coaster wheels (depending on which ones I have on the shelfs) on some and not on all of them.
Steel wheels works better than rubber or hard plastic wheels on most surfaces