Paul,
The shoring is relative to the weight of the object and the height it is to be supported at. A two ton block 1/4" off the ground could be supported by 4 1/4" steel washers, the same block at 3' would require 12 x 12 cribbing. If we were to support that weight twenty feet above ground level, well that's a whole different animal. Engineering would be required to safely accomplish supporting a load that size twenty feet in the air.
I gave you large enough footings for a crawl space of 3' - 6' granted if it was the latter we would use adjustable pipe supports bolted into the footings and a U clamp at the top to accommodate the lumber and possibly some cross braces.
At 18" sister up the joist on both sides so the joist is three wide. Drag in four concrete blocks throw some pressure treated lumber on top so you can use 3"x 6" oak wedges and make them snug. DONE.
You can also use the wedges to level the floor in that area. Most important make sure the stand is directly over the top of the triple joists. The reason I suggest triple joists is too have room for error setting the stand.
Yes 40" with a 10" overhang.
