To change or not to change...

Thanks for the input. I’d like to stick with the same block, since it is original and my parents bought it new. Doesn’t sound like it will be worth it without a major overhaul. What could I do to gain hp on a 273 block? I do remember on a previous build it was bored .30 over. (Not being a mechanic, it sounds impressive, but not sure what it means to performance. )