I heard somewhere that it wasn't much. I just want to know if I NEED to top swap it to make it fast.

I'm a noob so 300 horsepower is my goal for MY first build. Is this achievable? Am I shooting for the stars?

Also, there was a guy that stated "The conrods on the series 2 3800 are weaker than the crank and over time, the conrods will have turned into a slight oval" or something like that. Is this true? If so, I might have a bad engine (Not to sure on the condition of the engine but the previous owner didn't take care of this car at all [70 mph average with a clogged cat, bad bearings, random misfire, slipping transmission, and dexcool in the system])