400 with 440 crank

You essentially end up 426 C.I. but you have weak cast internals.
No not even close. A 400 has a larger bore than a 440 @ 4.342 vs the 440's 4.32 bore. Putting the larger 3.75 inch crank in a 400 nets a minimum of a 445 if no over bore, an overbore of .030 Nets roughly 451 cubic inches.

Plus, you don't do this with a cast crank. 440s pre 73 had forged cranks, easily found these days