Let me expand on what I mean by scan grain. Especially if you scan the film, what you absolutely must not do is underexpose this film. You will get much less scan grain if you err slightly on the side of overexposure. Only a half stop or so is what I mean by "slightly." Keep this in mind if you are looking for 800 speed and especially if you plan to scan. You can bracket if you don't believe me. Even if you do believe me, bracket and learn anyway
In my opinion, if you rate 800z at 800 then you need to develop it longer, e.g. treat it as a ~half stop push. I got very good results rating it at 1600, using 645 format, but it was developed as a 2 stop push... i.e. for 3200. My results, which I deem satisfactory in term of shadow grain, are in the apug general gallery somewhere, let's see, yes, here.