for 70% park, mostly rails, I think a 179 shreditor will be too big. K2 skis are always a little longer than the stated length so they will be more like 182cm long. If you're a really good park skier, you could probably handle it, but i'm the same size as you and wouldn't risk it.
If you're looking for a bargain, this might be it (174s), I haven't skied them but I've heard good things:
there's a certain point where it neither looks good nor functions properly...that's when you know you look steezy - no_steeze