corvette intake manifold

I have a 1970 base corvette. It's an automatic , 350/300hp. It's all original but I am considering modifying a few things for added horsepower, keeping the original parts so I could switch back if I intend to sell down the road. What are some things I could do that would help? I have looked into intake manifolds, headers and mufflers to pick some speed up. Will changing these things give me noticable difference, or would I have to go further with it? What intake will fit under the hood of the base corvette hood and fit the spread bore without adapter? I have a edelbrock 750 carb and like it's performance.