I haven't got a micrometer handy but I just noticed GIO list the chain as "KMC 428-116L"
looks like a 428 to me..
I think the cross bolt measurement on the sprocket is 67mm.. a couple weeks ago I ordered one of those $7 chinese digital vernier calipers.. hopefully it's here soon and i'll know for sure..
edit-- this looks like a close match,
http://www.jtsprockets.com/52.0.html...el_uid=5202&p=