I don't think that the Skyline or the Silvia have the same subframe as a Pulsar - the Skyline certainly doesn't because it has HICAS (which I quite liked because it only let you get a slide going if you really meant it, and caught you before you got into trouble when you didn't).
The Pulsar kit it pretty available, and I think there's a choice between whiteline and SuperFlex/SuperPro isn't there? If you're in Japan you should be able to get them from Australia relatively easily.
Correct me if I'm wrong though, because it wouldn't surprise me to find that the bushes are the same even though the subframe is different.