Mark from SSV was driving it for awhile before this was put up for sale. It's already in their yard when I bought my V35 off them in May. I used to go there once or twice a week to check the progress of my car for about a little over a month. So I have seen it in flesh many times. All I can say is overall it's a pretty straight R34 GTR. No major dents or marks. Engine looks ok with some minor mods. Sounds awesome too. 55k is on the high side but their cars are usually pretty neat. So they might have their reasons to justify the price.
P.S. If they tell you the Ks are genuine, don't believe them cuz Mark himself told me they are not.