My 1966 122 Auto has always done the same, spiking up to the red zone pretty much right away and even on colder days. On 90+ degree days stuck in traffic I would get a bit panicy when the needled threatened to disappear to the right, so there I would be with the heater on full blast, hoping neither my Swede or this Norsky died before I made it home.

I replaced the thermostat with no change, then checked the thermostat with the "boil test" and found it was working fine (and double checked I had installed it correctly). I ended up flushing and replacing the coolant from the radiator and the engine block. No change, but I think this was a good idea anyway, as some gnarly red-brown muck came out of the engine drain plug. I now do this regularly. Nothing seems to change the gauge reading, but I also have never had any radiator overflow (even on those 90+ days). I pointed a laser temp gauge at the engine, and though I can't recall the number, it seemed reasonable to me at the time (anybody know what temp range you would want to see when checking this way?)

So, I've developed a theory for my car anyhow, and that is that the temp gauge is off. Others on this forum have explained to me that the gauge is connected to the engine not with wire, but with liquid in a tube (a long thermometer?) that expands based on the temp. I noticed that the protective sheath on mine is a bit frayed, which may or may not be the cause. Because that liquid tube deal sounds like $$$ to me, I've resolved to leave it as is and hope for the best. I'll be sure to post if my engine seizes. =)