Never did much care for the round red knob on the heater pull. I had one on the last car so I thought I would do the same on the 75. Ordered a 911 pull knob BUT it is designed for the 914 72 only flat lever, so it was time for a little modification.
Got a drill bit out the size of the large hole on the round knob and marked it on the drill. Got second bit that was slightly smaller that the threaded portion of the inner hole and marked it too. Found the center of the 911 knob and did the drilling. Since the knob is plastic it became self threading and is just a matter of tightening it down.
Knob was $19 shipped on Ebay.