The general pattern of the market is that there will be very few cars on the market at a given point in time. Often for months on end, then there will be a period of multiple good prospects on the market within a 6 month period and then nothing again. Many of the cars that come up for sale are cars that were bought and sold a few years ago and people move on.
I suspect many cars though are in private hands with people planning to keep their cars. Given how few good ones are left, it seems the cars that show up most often are the projects in need of rust or damage repair.
Everyone wants to put an RB in 1 these days, but I would urge anyone thinking of doing it to first drive a well sorted L-series powered Z first. They are a lot of fun, even at 150-200 HP.