Well from the education I got from my builder, the Dart aftermarket block (short deck) is capable of alot. The tall deck is capable of even so much more, 2000hp NA or blown. He builds alot of Tractor Pulling motors that need big Torque - STROKING it is where it all comes from....
The GM Gen 6 block (502) is what I found and has forged steel internals, so its good to go, just needs new bearings and a hone to freshen it up for another 100K miles and a good cam to make 500 ponies easy. It would be a very low stressed motor at that point.
If I do go 565" with a new crank stroked to get 700hp and maybe 660+ ft/LB torque with new heads, valves, cam, intake etc, its a whole new ball game, but still a block that can handle it easily at a 10.5-1 compression ratio. just more $$$