It is not a matter of how much Jax plans to build into the engine. With turbo/supercharging, fuel choice and nitrous enough torque can be developed to overpower about any block. What Jax is asking is how much torque which is a factor of cylinder pressures developed and vibrations. A main girdle ties the main caps together to change their natural frequency out of a range that is a multiple of the oprrating RPM.
The SBF is recognised in stock form to be limited to 500HP before the block can split. Modifying for 4 bolt mains, reinforcing the lifter valley and filling the block to the bottom of the water inlet holes can increase the capability to 1,000HP.
The Mopar blocks are more substantial, but heavier. Assigning a value is a sort of vague statistic. Tune is a big factor, but small differences in volime casting can allow one block to survive while another fails, even with identical build specs and tune.
I believe Jax is asking how far he can push the envelope faily safely.