I know exactly which 240 you're talking about.
*Link removed upon possible buyer's request
I was going to try and sell my car quick so I can snatch that one up... But then I realized that it's going to be hard getting the car to pass emissions.
I say go for it for $5500 if you have another daily driver. The car looks sweet. It already has the SR motor in it and if you have $1500 to spare you can make it look even nicer by doing a silvia front conversion and slapping some kouki tail lights. If you get both done by Oct 12, you can show it off at IREV and possibly win the grand prize and get some money back.
BTW, there's another SR20DET 240sx on Craigslist for $500 more.