The a6 is out of a 88-91 crx or 89-91 civic si.
The z6 is out of 92-95 civic ex sohc vtec!
Truthfully if you have access the 96 and up Y8 motor would be much better and probably have less miles!!
But to answer the original question Chahonda I believe has done this swap!!!
Sohc's are coming to get dohc's!!!!!!!