A 350 or a 383 will be sufficient to make the 500 horsepower you're looking for. If you really want to do forced induction, the better of the two would be a 350 for compression reasons. A 383 is the same thing as a 350, except with a 3.75 stroke as opposed to a 3.48. Naturally aspirated, the 383 would be about the easiest to make more power out of, but can be more expensive depending on the internal parts you want. Of course, a longer stroke has further to travel to accomplish the same 360 degrees of rotation, so yes it will rev up slower unless you spend the money to get the lighter parts, and internally balance your rotating assembly to reduce rotating mass. Any type of forced induction will make good power, but for 500 hp, I would say that you're going to have to search for a good price on some type of forced induction, because in most cases a lot of your money will be tied up in just the system. I'll give you this just to help you to decide, if you take that route. Twin screw type and roots type blowers are for lower rpm applications, at higher rpms they're spinning too fast to make boost efficiently and become more of a load on the engine, not to mention that superchargers are rated at a maximum rpm that they can turn, this limits boost and rpm of the engine. Turbochargers can be mixed and matched to find the rpm ranges you're looking for, but you will always have what is known as "boost lag" which is the time it takes the turbo to accelerate up to the point to where it actually making boost, but it can be a good thing sometimes. A turbo though has almost no limit to rpm that it can turn, though another down side to that is that the higher rpm you want to run with a turbo, the longer you're boost lag will last, unless you use more than one turbo, each of a different size, but the money is adding up at this point. A turbo as well as a centrifugal supercharger will require a blow through carburator, which is a carburator that you can buy modified this way or send off your carburator to be modified this way. If you're using an injection system with any type of forced induction some tuning will be required to make the maximum amount of power, of course, but usually just to make it work you'll need tuning and maybe some changes in components used for fuel delivery, sometimes sensors will be a factor as well.