I've always been of the impression that these Pro-Tec pipes were optimized to mount to Pro-Tec heads using both mounting holes in that tab coming off of the chamber. They should align with the raised (and threaded) areas that are a feature of the Pro-Tec head. A search of images on the 'net appear to support this.
Probably worth scanning the 'net for images of this pipe mounted to a stock head. If it looks simple the stock head option would probably be the easiest/quickest/cheapest solution.