Help with engine decipher.... please

[69camarokid]

Hi beautiful people!



My dad is turning 60 soon and I am making some modifications/improvements to his 73 Nova.
I'm having trouble figuring out what to do with his Chvy 350 engine. Its lethargic and underpowered.

I could do a crate engine, but that would eat up the entire budget for the whole car. Id rather do modifications.
He just wants 300 HP out of the thing to cruise in. When we bought the Nova 12 years ago we were told the original 350
was replaced with one out of an 80s Camaro Berlinetta, which leads me to believe the engine may be a 305 ( oh no!)

I asked him for the casting numbers on the black and he came back with 70201041. I can find nothing on this number anywhere?
Thoughts, ideas, ... anyone know any easy way to tell. Really want to help my dad out and get him an awesome birthday gift.

Thanks!