I don't understand how the square-cube law is relevant here. The volume of blood indeed scales cubically with the length, but so does the volume of the heart. Where is the quadratic part of the equation that limits the maximum size of a whale? Why would it not work to take a whale and arbitrarily scale it in photoshop?
> Where is the quadratic part of the equation that limits the maximum size of a whale?
Muscle power output increases with cross section area, ~L^2, not with volume. The heart have no separate power unit. It relies on the same muscle walls that comprise its chambers to power itself.