The two that I have are def not interchangable. The spacing on the crx rails is much wider than my civic. I'd have to change the seat pans in from the civic to the crx seats if I wanted the crx seats in.

I'm more interested in a seat mount adapter to fit a fixed back seat. They are available from the US but as they list 88-89 as a different mount than the 90-91 I'm not sure which fits the Aus civic if either. The pictures in the ads seem to be generally non specific or not suitable.