Hi Drew,
If you're looking to use the BA light you will have to use all the falcon mounting gear- the foam surround and light mounting plate as well as adjusting the wiring. I hacked off the original light mount. Takes a bit of jiggery pokery to get it in but is a snug fit and looks neat, This was all planned prior to fitting the headlining. Will take a piccie and post it up , I think I had to make up an alloy bracket to hold it up and screwed it in place of the original.
Remember this is my build in reverse, car is already on the road. Was busy over Xmas anyway, stripping and prepping those door trims you organized for me. My wife had to sweet talk me into buying a sweet pair of Alpine Type R splits for the front doors as my original old set have pretty much given up the ghost. It's amazing you couldn't hear the screams of pain from the West!! She said with all the money spent on the RS so far why not get something good, she knows I like my music cranking. Cheers, Len