Even easier and cheaper, the tried and true 350/350 combo.
SBC 350 bolted to a TH350.
3.42's in the rear end and she will, as the old song used to say, really get lost!.
Nice thing about the '68-'79 Nova's, the engine bay is large enough to fit anything.
From a 153 four cylinder to a 632 big block, there's plenty of room.
However, you say you want the HP & Torque, but those terms are relative.
What are you starting off with?
A fresh 350 4-bbl/350 combo I mentioned, compared to a worn 305 2-bbl and Metric 200, will make the car seem like a rocket ship.
However, if you're already starting off with a modified engine/drivetrain, then you're obviously looking for even more power.
So what do you have right now and what kind of "improvements" are you looking for in a drivetrain, and maybe we can help you better.