I do not have a Pro Mac 72 (yet) but I do have the Titan 50, 57, and 70 models and they all use the D176 bar mount if I recall correctly.
I do have an IPL that lists both McCulloch and Electrolux part numbers, for the spike they show 538241169 which is a Husqvarna part number.
If you start to Google search I expect you can find a lot of information if you're willing to sift through it all. At least one source identifies the bar as a D009 mount but also lists it as fitting the PM55 and PM60 models which are certainly D176 mount models.
Mark