increasing block strength

If I were trying to build the most power with, for example, a stroker 440.... I would start with the strongest thickest casting I could find, bore it the minimum amount, consider a main cap change depending on what kind of power adder, either aluminum or steel caps, a partial fill, and a girdle.
Machining costs will add up quickly, but not near as much $$ as an aftermarket block. The question, that I don't know the answer to, is at what point does the bandaids to a stock block become not enough, and a aftermarket block become mandatory? I have a buddy who is building for 2000 hp. He's using a solid aluminum tall deck KB block.