what engine can i put im my project impala 63

You can swap just about anything in there. Go join a Chevy Impala forum and just lurk for a while to pick up some ideas.

A 350 SBC is what most people do. If you still have the original engine you should use it as the car is more valuable with the correct engine.

Keep in mind the old 300hp engines were probably more like 250hp because of the rating system used back then. If you want 300hp as measured today you would want a more powerful engine (at least 350 hp gross) which is not hard to buy or build. 300 hp at the rear wheels would require something like 375hp net at the flywheel.

If this were my project I would buy a fuel injected Connect and Cruise engine from Chevy. A FI engine will be much better on fuel. https://www.chevrolet.com/performance-parts/crate- engines