Well, here I go again...

I've replaced almost every component in my cooling system (1983 300cd T) with new, good parts and am still experiencing temps around 90C and sometimes even 100C in the past few days. All the following have been replaced:
-Temp Sensor $20
-Temp Gauge (incidental, not as a fix) $20
-Radiator $200
-One thermostat was bad, the one in now is good. $40
-Expansion Tank Cap $7
-Water Pump $80
-Fan clutch $50

Over the last few months I've been using a hollow thermostat body to hold the seal in place with the mechanism drilled out. This worked and kept the temperatures at 65 city and 80-85 highway. A few days ago I put in a new thermo since I found out the system is designed such that the thermo is not just a straightforward open or closed deal.

So now I put in this new thermo, which I know is right on the money, and my temperatures rise again to around 90C and up to 100C. I don't think that my cylinder head could be cracked because the car runs great and I'm not losing coolant. I don't think that my water pump/fan belt being a little too tight or loose could produce this pronounced an effect. There's no way any of the parts above are bad.

I did read in the 123 engine manual that there is an arrow on the thermostat and it should be pointing up...I didn't do this, could this be my problem? It doesn't seem to be an air bubble because I can't feel any in the upper hose.

__________________
"I would rather be ashes than dust!
I would rather that my spark should burn out in a brillaint blaze
than it should be stifled by dryrot.
I would rather be a superb meteor,
every atom of me in magnificent glow,
than a sleepy and permanent planet.
The proper function of man is to live, not to exist.
I shall not waste my days in trying to prolong them.
I shall use my time."

-Jack London 1876-1916

1983 300CDT (running WVO since 12/05)
1981 300SD (parts car)