...actually if it's an .img file won't it write over everything on the SD card??
Yes it will. Images are complete systems, you are looking for packages.
My advice is to stay with a "neutral" distribution image, install latest dump1090 mutability, and then just add the feeders that you like.
I use DietPi for a very lean distribution, but NOOBS / Raspbian should work just as well.
Then install dump1090-mutability, check that it works and provides raw data on port 30005.
Now you can install all the different feeders you like. Don't let any one of them take over the decoding, just direct them to localhost:30005 for data.
This will provide the most flexible receiver setup, without too much dependencies on the different sites own software.