It is kind of bolt on. The turbo mates up to the manifold and dump pipe and the outlet I believe is also in the same place. You can use all your old oil and water lines. However, the gen 2 bracket that holds the turbo does not fit and requires modification (welding an extension to it then drilling a hole in the correct place for the turbo thread) and the heat shield also needs a hole drilled in a new place..
I actually have a CT20B that I've just removed from my racecar - it has the following modifications:
- High flowed wastegate ports (stock ports are undersized and will overboost with a 3" exhaust)
- Clocked the compressor housing, complete with new bracket to hold new Turbosmart IWG75 dual port actuator
- Elbow welded on to outlet so that connection is easier and it clears the clutch slave
- Modified Gen 2 turbo bracket (extension welded to it then drilled) to match up to the turbo
- Ceramic Coated (high temp black) turbine housing
- Repainted (silver) compressor housing
So if you are interested in a CT20B and want to run a front mount intercooler (hence the clocked housing), mine has all the work done already to just bolt on. I'm in Australia though so shipping would likely be a bit of a killer.