Interchangability Impreza and Legacy struts
 

Does anyone know whether Imp struts will fit a Leggy?

Depends on year of Impreza/Legacy mate. Some will and some won't.

I don't know all the specifics, but classic impreza stuff will fit classic legacy and vice versa.
See this thread for more info:
Legacy/Impreza Interchangeability - UK Legacy Forums

And if you want Legacy info in general that's not a bad site to look on. ;)

Regards
Jim