The C2T IC does fit a 930 without any problems, so long as you remove the AC and the rear wiper motor. You are correct about the turbo-to-intercooler hose (930 110 368 00). It currently costs $300 alone, and that's the price from Pelican. I'm glad I bought mine a few years ago when the price was about half that!
Another option would be a short aluminum transition that tapers from 2.75" at the turbo to 4.0" at the IC. Not sure if those sizes are accurate, but you get the idea. That tube could then be connected with short sections of straight silicone tube.
My 1981 930 with a factory C2T IC installed:
