A 600hp 383 is 1.56 hp per CI which is pretty stout. Since you do not want to run any boost, your best bet would be to use nitrous. However, with those KB pistons (Im guessing hyperutetic) it wouldnt be very safe. Also, are the pistons notched for valve clearance? Because without notches you wont be able to run a cam with a high enough lift to net you that 600 hp. You are also going to need one hell of a set of heads and an equally radical cam. Also, you said you wanted it driveable....that isnt going to happen without a power adder and even then, it wouldnt be that streetable. You probably will end up rebuilding the whole thing and having a ton of money in it if you choose to go that route. If it were me, I would find another B-block (preferably a 400) and make a bullit-proof stroker out of it. In the meantime, you can use that block to build a very steetable 383 with 400-450 hp and easily run 12s.