Putting a value on a car is very difficult. We cant help looking at what we have spent when we try to come up with a price. Projects like this were built with the intension of keeping therefore we tell ourselves that it doesn't matter how much it costs. Then when you come to sell, you realise you've spent several years building a car and working on it for free, then sell it for well under cost price.
I think when selling a car you have to price them as you would when selling a house. At or below the market value. If you price it too high and it doesnt sell then you will normally have to reduce it to below market value to generate any interest again.
From all accounts, this is a superb car and probably one of the best in the UK. I'm not going to get into the original RHD or not debate because, as Sean has said, every car should be judged on an individual basis. I'm just not sure who will buy it. The inverstor will probably want an original (RHD or LHD) car or one with racing history maybe. An enthusiast who wants to drive/use the car may see this as the best of both worlds, being rust free cali car and RHD, but feal its too good to be able to use. The Jap tunning companys who all want S30's to go with their GTR's and have big money to spend, won't like it because its lacking in performance mods.
I think the yellow/green car Sean posted for sale is where the biggest market is and in my opinion, the perfect car to buy/use.