At that point if you would get custom pistons, (because with the exception of KB240 there are no 400 stock stroke pistons) and the would be lots of $$$ I would be cheaper to get a 440 steel crank ground down to 400 mains and counterweights cut down use 440 rods and 1.32 CH pistons that would be readily available. This makes a great combo. Torque is unbelievable. It all depends on how much $$$ you want to spend and how much power you want. Het I've done a 470" 400 that would pull trees down LOL!!!!!!!