There are many different ways to get a heart scale.
I'll list them for you:
Beatiful beach - 2000 steps
Warm beach - 3000 steps
Stormy beach - 800 steps
Quiet cave - 2500 steps
Ruins of alph
Wild pokemon holding heart scale:
Sunday for 2000 points.
You can also somtimes find them using the dowsing machine.
When you get a heart scale, go to blackthorn city and ask the fat guy to teach ancientpower to piloswine.
Then level it up a bit and it should evolve.
And, yes these are the only ways to teach ancientpower to piloswine.
Hope this helps.:)