Would you happen to know if the rear Bembro caliper and mounting bracket is a bolt on for a 2007 Road king? Thanks.
It is not. But it's close if you want to.
2007 still used the 1" diameter axle. 2008 went to the 25mm axle. That's 0.984". So the axle hole in the mounting bracket for the Brembo caliper is too small.
I've mounted several though. Both of my older brakes and several others. If you've got a drill press, a 1" bit, and a simple brake cylinder hone you're good to go. If not take your existing 1" axle (from the 2007 bike) and the new-to-you Brembo bracket to a machine shop and ask them to bore the hole in the bracket to accept the larger axle. Aluminum and steel don't expand evenly at temp so I shoot for about .005" when doing these.
The parts you'll need are few. The complete caliper with its brake pads, hardware, and pins. If you're buying a used one just make sure it's all there as it would have been removed from the bike. You'll also need the the mounting bracket (that's the piece the axle goes through) and a rubber bumper that goes through it. And the brake rotor. The rotor is just a slightly larger diameter with the newer setup.
Your original brake line will connect up just fine. A couple times I've had to release the hold-down on the original line to get a little more length before tightening that hold-down bracket back down. Have never had to replace the brake line though.
The pic shows the parts you'd be after. Just to compare against eBay images or wherever else you might be shopping.