sizing will depend on what you want from the turbo. if you are retaining stock boost then any moderately sized intercooler will do. you're going to have to manufacture piping tho to plumb into the system. a smallish IC should run you around 5-9k and then the plumbing will probably go for about 5-12k depending on the material (black iron or stainless and the diameter)

expect more lag sa system tho if you install an ic when there was none before.