what do i need to do to make around 450-500horse out of a 351W . block already bored 30 over. wanting to put on aluminum heads . 10.5 to 1 compression. need some ideas on what type of heads and cam to use to keep it where i can use pump gas 91 octane.  

I'm no expert, but 450-500hp on pump gas is a pretty tall order. I would think you would have to punch more cubes into that 351w or supplement a strong build with some nitrous to get there. Considering that the 302 you are replacing probably made 200hp or less,(stock,) you can see you're going for some serious hp. Are you going drag racing? Unless you upgrade your whole drivetrain, I think you'll be breaking parts. You can get a stroker crank that uses stock 302 pistons and stock length 351w rods and get 393 cubes out of that 351w. I'd do that, use an Edelbrock Performer RPM manifold, heads, and cam kit, or similar, a good aftermarket ignition system and a set of headers, and live with whatever hp that makes, (probably @400 or so, maybe more.) This set-up should give you some good torque, and live happily on pump gas as well. Just my opinion, but I hope this helps some and good luck with the build.