I found my 187 at a wrecker. The 187 is stamped into the pan and the numbers are 2 inches big and are the last 3 numbers in the Mopar P/N. The later model land yachts 72-76 (I think) used them with the 400 and 440's. I used the Schmacher system to put my 383 in the 71 demon and it works fine especially the Tri-Y headers. There's also a section of their website that talks specifically about the 187 and 699 oil pans. I'd also recommend using the Milodon windage tray on that engine.
Good Luck :burnout: