Identifying a nissin caliper

[thredbo]

My front caliper on my wr426 needs a rebuild and new pads. I bought the bike in motard trim and I'm 99% sure the caliper is larger than stock (compared it to the one off my parts bike).

 

I tried running the serial number off the brake pads through Google but got no results. Any other ideas? The only markings it seems to have are these:

[S.O.A.N.Z]

3D7 08-11 WR250R

http://www.boats.net/parts/detail/yamaha/Y-3D7-2580T-10-00.html