In theory this may be true, but a B1 headed 400 would be challenging getting the valvetrain to live past 10K RPM

Finding a block would be a challenge these days I'd think as well. On paper you'd be right.

Deck height would want to be 9" or there abouts.

It's not a combo that hasn't really made its place in Super Stock or Comp, the destroked Hemi 99 engines in Comp have seemed to be replaced by the P5 stuff