Let me describe what I use.
First, measure the width of the tread on the tires and then add 1/2 inch to that, then go to the next board size (width)
IE: if tread measures 9 inches, 1/2 inch is 9 1/2 inches, next standard board width is 10 inches, so use 2x10's
First
Second step
Third wooden step
First step is a foot long (In my case it's 2 x 12's by the way
Second step is 2 feet
third is 4 feet
Stack them and drill down, through them so as to stick a couple dowel rods down the holes (I drilled down through the 2nd step into the third, then flipped them and drilled the same holes into teh top, then cut the dowel so it stuck up out of the 2nd step about an inch when fully inserted.
Slather the bottom of the 2nd step with wood glue, lay it on top of the bottom step and insert dowels in holes,
Slather bottom of top step lay it over the dowels and tap down with rubber mallet.. Jack up towed and set it on top of the stick to Clamp.
My second set has only the two bottom steps.
That way I can put I am considering a 3rd pair when I get the engine fixed.
Lay in front or behidn tires, back up or pull head to level.. NOTE> DO NOT drive off the high end. (Im considering a stop board there.