I have the Wolo Air Horn works pretty good with 139dB and the install is not difficult. I installed it in the stock horn position but plan to move it to the left side (choke valve location) because I am getting the reaper shroud, hope this helps.
I have the compact Stebel horn and painted the compressor pump matte black. I also separated the horn from the pump and mounted the pump behind the radiator fan horizontally on the bottom frame (instructions say to mount vertically within 15 degrees, but I have had no problems). I mounted the horn below the choke pull on the descending frame.