Re: Will the Garmin 7616xsv fit in the 306 retractable ebox?
Yes, I'm sure they can do anything you want, but you may want to have them pre-cut all the holes which will make it easier for you to install the electronics. My box used to have two 12-inch SIMRAD displays so when I upgraded my electronics I needed to cover those huge holes, and my Garmin had a differently shaped cut out.
As for the gauge panel, I don't think they will have the template already, but have a chat with them and I'm sure they can figure it out. I had the same issue -- I went to the Yamaha Command Link + digital display, but I ended up leaving the old round gauges in place and they even work too. It turns out you can run both gauges. I also thought about replacing that panel with a bit of storage for phones, sunglasses, etc, but in the end I just left it.