So, the tachometer was wrong. The first independent RPM measurement was also wrong. The nifty add on Tachometer I bought today (only 8 years too late) unsurprisingly was correct.
Adjustment screw located and now the RPMs are normal. Bonus repair: now the clock and tacho lights illuminate.
Result! I'm now suffering from severe steering wheel envy! Look at that, it's immaculate. Great colour too, that pale yellow. I'm not a huge fan of wire wheels, but they look just right in this instance. Your car will look absolutely perfect with your new number plate. If I ever make it over to San Diego I'd love to go for a spin down the coast road in your car. Keep those pics coming.
Were the problem not to have been solved, there is one other (unlikely) possibility that you guys missed.
There were TWO final drive ratios available for the 2000 and 2000TC.
Standard was 3.54:1 as everyone knows. But optional was 4.1:1. Developed for the rally cars and homologated, so it had to be made available to the public for that to be done. I am aware of one car known to have that diff and I've no doubt there are others too. The low ratio diff seems to have gone along with a gearbox with a LOW ratio third (1.51 instead of standard 1.391:1)..........
And whilst on the subject of homologation, did you know that 5 1/2 J steel wheels were available from 1964............ Part No 562041.