[TomP]

Or get an aftermarket block , bore it to 4.41" and use a 360 crank to get 427.

I have two worn out .060" over 390's that barely clean up going .080" over. Bored the one to 4.13" without a sonic but i figure if they've already been running at that size what can it hurt? Of course the walls might be so thin they bent out rather than wore that much.