What type of power needed to compete, with a 427 chebby? (Not stock 427)

A twin turbo SB would be killer at the strip. On the street you'll be in trouble because of spool up and not a full quarter mile. A 440 will leave on a 427 but it will come back toward the end of the quarter mile. I believe a 408 with good heads and cam and a good converter is mandatory in an A body and will beat the 427. 650 HP from a 427 is a really strong motor. I can't see it being a street motor or that much HP for $800. Have you seen the dyno slips? If not, I would bet it doesn't make 650 maybe 550 or 575 at best.