The brakes may fit,but it wont be quick or easy. The v6 has ap racing four pot callipers I believe, probable with 330mm discs.
First off the V6 has a five stud arrangement, so the disc will not fit straight on to a 172 hub. Im not sure, but if the V6 uses a two piece disc (separate mounting bell) you should be able to buy a new mounting bell with the correct fitting. If it uses a one-piece disc you would need completely different ones.
I doubt the v6 uses the same front uprights as the 172. If the callipers are radilaly mounted you will need new mounting brackets machined to fit the callipers to the 172. Disc offset may also be a problem if different uprights are used.
If you are interested I can send you pictures of correct mounting brackets to fit standard brembo or ap racing callipers to a 172. I can also tell you exactly what dimension brake bell is needed. If enough people think it is usful I can produce CAD drawings or the parts (to fit 305mm discs or larger if required).