very few 16" wheels can fit over the willwood kit, and no 15s. Seeing that 17s are a bullplop wheel size for any purpose, I'd steer clear of the willwood kit.

I'd do: brake fluid upgrade, brake pad upgrade (Hawk HP+ and Axxis Ultimate are good choices), steel lines. If that doesn't tide you over, check out the fastbrakes.com packages... just as good or better quality than the willwood kit, cheaper, fits under 15s.