a little harder to find, but the newer ls7 from the 2006+ zr6 vettes would be a good choice. a 7.0l v8 pushing around 500hp stock. getting it to 650 would be easy from there, plus the crank and berring caps are forged steel, and con rods are forged titanium, and
hypereutectic pistons.
just a thought if you went that way. id go with the 2jz myself,