It's DIY all the way I'm afraid. A good Volvo 940 intercooler fits well in front of the rad and look here for some stainless tubing....
http://www.nissansilvia.co.uk/vbb/showthread.php?t=1947
And here for some Silicone hose...(and pipe work)
http://www.nissansilvia.co.uk/vbb/showthread.php?t=1616
Probably best to go for an electric fan as well to make yourself some room and gain a little bit of power
