David, i've moved a 10' x 12' building quite a distance with a tractor, but no experience with one as big as yours. It sounds as if you have the right idea, but I don't know about the weight involved. Are you doing to move everything out of the building or will it still have tools and such in it? If you put 4 x 6s under it, will the front ends be tapered? Of better still can you lift the front ends with either the front end loader of the 3-point hitch to move the building? How many 4 x 6s, how far apart? How will you keep them the same distance apart as you go?