Again, much has been posted on this, including a detailed list of stuff from me a few years ago, but the easy way to get a decent soundtrack is to get a miniature mike for the camera and tuck it under the headset earcup
It helps to have a cam which has a
manual recording level control.
Headset / intercom connections are the best, and tidiest especially if you want to mount the cam somwhere and not interact with it during flight (the safest way; do the editing after landing) but you get a really good result using the above, with an ANR headset.
I am into electronics but have always found aircraft mike arrangements a bit of a black art and fiddly, so I stick to the miniature mike solution.
Maehh - you want a 3rd Gen image intensifier on that cam