to get 300 on 87 octane you will be able to buy a kb blower and then some with the amount of money you would be spending. kb route would be alot cheaper, but you still need a custom tune and higher octane
i think 13.8-13.9 at the most with an auto. you need to focus on coming off the line harder. stickier tires, and a torque conv. will easily put you into the 13.3-13.6 range. also maybe think about getting a 4.10 with an auto instead of the 3.73