We really appreciate the thread, pics and narrative and we (I) appreciate your energy and thoroughness. Early on, you started to get a sense for why these cars are so believed. It's because of the driving experience, frankly. Lest we forget. I drove mine twice in the last two days, which I rarely do, and it is just SOOOOO much fun. My car is set up perfectly, for me. Particularly the suspension, wheels, tires and cams.
The first pic of your removed fan made me think it is the correct, and fairly rare and desired by racers, fan. The other pics make me unsure.
AFAIK, all 1978 USA cars had it. The fins are shorter than ordinary 911 fans, and I think the entire diameter of the fan may also be smaller. The fan and housing are a pair. It is the fan that went on the earlier RSR. 1974? I think it actually moves less air, but also robs less power.
The plywood pedal plate is great, and functional, and very light. Too bad yours was toast. Other parts, like the cardboard ones you replaced in the trunk, follow a similar design decision. Lightweight, and built to do the job. All those parts, on cars not subjected to water in the interior, are just fine after 45 years.
Though mine is not currently working, I do like having cruise. There is supposed to be a sticker on your lower dash showing the elegantly simple way your cruise stalk control should work. Similarly, the intermittent wiper design is the best I have seen in any car, period.
You are doing all the right things. Troubleshooting a CIS system begins with checking fuel pressures. Swapping out parts is not the best way to troubleshoot a CIS. Your fuel pump may be delivering inadequate pressure or volume, but generally they either work or they don't. That said, I would suggest replacing it. Factory original ones are nearly a half-century old and ignoring yours might be a good way to get stranded at the most inconvenient time and place.
Happy motoring, and thanks for the updates!
Oh.....I installed headlamp relays. My high beams are 100W. Just like having daylight, at night. I see you have the Euro H4 headlights. Nice car!
And yes, absolutely, backdate that heating system. One of the best of all possible upgrades for this car.