360 pros & cons vs 318

There's no replacement for displacement. All else being equal, a 360 being 13% larger will produce 13% more torque/power. In actual practice, a 360 will produce this and more over a 318.

When you say stock bottom end, do you mean stock 318 cam?!?

The late 360 heads and big runner intake aren't the hot ticket on a mild 318. Without knowing what the rest of your combination is (cam, gears, converter, etc...) it's hard to say how much the 360 would help, but it would.

Forget the 413. By the time you factor in all the things that must be changed for a big block swap, you could probably build a 408 stroker and go faster. That seems to be the current trend, and for good reason.