Motor Dolly suggestions

I made one from wood, and some heavy duty steel casters.

Here's how: make a two x four wood base like a furniture dolly about 2' x 2 1/2', - then screw 1x6 yellow pine tongue in groove on to that to make the base. Next I put two 1x10 uprights a couple feet long spaced apart far enough for the oil pan to slip down into, which the pan rails sit on. Added some 1x gussets to the sides of the uprights and some end caps to the uprights on either end. Used dry wall screws and construction adhesive to assemble it. It has served me well and shown no instability. It doesn't get used for joy rides anyway, and I didn't have to buy a welder to build it.