Well, I can share my homework with you. I'll have to fab a bracket, but it looks like the horn assembly will fit where the oem unit is. The compressor will fit beside the fuse panel or under the rear deck, just forward of the tail light assy. The rear mount is pretty cramped and at a diagonal. I think I'm going to, for now, end up with it beside the fuse panel and ziptie in place.
Today, while installing the hand warmer setup, I ran the wires (should only have to run one) that will go from the oem horn plug back to the relay that will go by the compressor. I also ran rubber tubing, all within black wiring loom to keep things sano. Next weekend I will try the final install, once I can locate a socket for the relay. 6 autoparts stores in Waterville and the only one that was closed appears the only one that carries them.