I had a JPI EDM-700 with fuel flow installed in my Cherokee Six 300. Since I was spending money on a new (to me) engine, I decided to upgrade to the EDM-830 so that I would get RPM and MAP and the USB storage (since the 700's serial download was getting to be a pain to do).
I am currently waiting for my engine, but I did go and install the EDM-830 in place of the older 700.
My EDM-830 is installed in the right radio stack (which is to the left of the glove box). I drew up a template (in Adobe Illustrator), printed it out, and then cut some 0.050" aluminum to make the instrument plate.
I have a photo of this on my blog (before and after) which I can send you if you are interested.