So, I didn't really get into this because it was kind of a general question... but here goes...
Like I said before- an engine is nothing more than an air pump If you stroke the engine(add cubic inches) and push more air then then you have to increase the air going in and increase the air going out. Increasing air going in means you have to evaluate the carb size, intake, valves, heads and cam(intake). they all have to balance out otherwise it's like pouring water into a funnel, you'll get a restriction. As soon as you get a restriction then all your money and time went down the drain because you'll lose horsepower.
Once you get all the air into the engine then you have to get it out as well. Which means you have to evaluate the cam(exhaust), heads, valves, headers, collectors, mufflers. And again, if you get a restriction then you'll lose performance.
Last you have to consider what is happening not just at full throttle but also at low and mid throttle. So you can't just go bigger on everything because that may slow down airflow at low throttle and mid throttle, which is where most cars spend their time. Moving air through the engine requires volume AND velocity. Get the ports too big and you gain volume but lose velocity. Make them too small and you gain velocity but lose volume. It has to be balanced. Most cars spend very little time at wide open throttle, and with 450HP I doubt you'll ever be there for more than a few seconds at a time.
So while its easy to say 'do I have to xxxxxx' the answer is that everything needs to be evaluated from the bottom to the top. If you don't then sure the engine will run and make more power than stock, but it won't be everything it can be and you'll lose power that was there for the taking if parts were chosen correctly. That's why I seriously suggested getting an already built motor. If you aren't understanding how all this works together then you'll have a tough time choosing components to build it up on your own.
The gas pedal fits best right up against the firewall, so I figure it should be there as much as possile