Not really, Theirs tons and tons of good people on here who can offer you a Skyline in whatever state of tune you want. I say go to the trade forum and post your qustion there, your bound to get a good deal!
If a GT-R has uprated suspension, then the standard suspension difference is negated anyways. There are a few extras such as the rear diff and dash, but essentially not a lot.
Quality, spec, mileage, etc. is different. Definitely make sure you're getting quality, as there's a vast range of rubbish out there. I took months to find mine, but eventually settled on an example from: Newera Imports - home / stock available