What if you took a factory block, and bolted a cylinder "extension plate" between the deck and the cylinder head, than you could increase the stroke of the block :D I guess the first limit would be that you couldn't go any longer in stroke until your rings got to the top of the deck, but if you wanted to go even farther you could sleeve the cylinders from the rop of the "extension plate" all the way down the bore. This would also require "intake extensions" since the heads would be farther apart. Also you might have to use some block filler in order to clearence the block enough for the connecting rods. Am I crazy or would this work?

What are you after? There might be another/cheaper tested method of reaching your goal, like using a tall deck block.
There is capability now to go over 800 cu. in. with 1 piece blocks, so IMHO why would someone want extensions and try something that is untested.

It would also require a custom fabrication for an intake manifold as well as specially made headers.

I know of a SBC that was done this way quite a few yes. ago, longer sleeves were used. The engine ran good, the chassis was a big issue though. This was in a FED w/ approx 210" wb and it never made a full pass that I know of.

But with the taller blocks available today, there really isnt any reason to do this.