Build a 9:1 400 base aluminum head 496 and you can make your goals on 87 regular. Not sure if this will be the hot set up for an autoX but if compared to an all iron SB maybe not so bad.
My 440 based 493 came in at 8.97:1 and it makes 500hp/600ft/lbs all done by 5500 and it does fine on regular. Over 500 ft/lbs from 2000 to the end.
