The term "HC-C2YL-1BF" only describes the hub, it tells nothing about the blades, so it is not possible to answer your question with the data provided.
This is a compact hub and would probably require a 4" prop extension. Your buddy probably uses a prop extension already, and while this is perfectly acceptable with a fixed pitch wood prop or even a lightweight C/S prop, it is hardly going to do a heavy weight Hartzell prop any good.
The recommended prop for a 320 is the extended hub HC-F2YL-1F/F8468D-14,  F8468D-14 being the blade designation. This hub is 4" longer than the HC-C2YL-1BF, the extension is simply built into the hub.

More info at: http://www.hartzellprop.com/kitplane/index_kitplane.htm

What your buddy needs to do is:

1. Measure the hub to verify that it will actually fit his particular installation ( I don´t think it will)
2. Find out what kind of blades are in the hub
3. Check with Hartzell or Lancair if these blades are approved for a 235/320 and can safely be cut down to 70"
4. Be wise enough not to take advice from "experienced pilots", "clever guys" auto mechanics or other smart%sses

Regarding props, cranks and a few other items, it is best to let the manufacturers do the experimenting!

Very best regards
Tim Jorgensen, Denmark
360FB  1992 - 2005, 55% done (good enough Scott?)