first of all how much cash you got for this build? this could become a factor in your choice.. I would go n/a 408w... just plain and simple, also i hear KB's tend to heat up? You could get into some big money going KB, My choice 408 NA .. money for money 408 wins vs a blown motor and power for power.. I cant see a 351w kb pulling a 408w if both motors are street motors. But if your just going for that whistle sound you might wanna get a stock 302 and just stick a BBK thottle body on it
... good luck..
why not 408w with a efi plate system
you got your mpg and your button for power