Do you have a RWC for it? I'm just about to put an R32 GTR on the market myself, although mine is almost stock. One thing I noticed while researching values is that not one of the GTRs I looked at on carsales had a RWC. I didn't look at all of them, but there were certainly a large number of cars being sold "as is". I would never buy a car that didn't have a RWC and I think it is only fair to have one prior to even advertising it online. No one wants to get jerked around waiting for you to sort out a RWC; if they have the cash they will want the car immediately.
Good luck with your sale anyway, remember it is only worth what someone is willing to pay for it. Most cars are not investments, you will typically lose a lot of what you have put into it.