Ok. So where exactly on the block did you try to install this sender? On the oil filter side? Access must've been a beeacchh.
Also- did you check out the engine coolant temp sensor at the water pump? When you think about how the sensor probably works, it might use a resistor (a thermistor?) that sends different values based on temperature. I guess the only thing that's lacking in the stock temp gauge is that it's not graduated & it doesn't look very cool. That Autometer is a good gauge. Is it able to be calibrated? How 'bout getting some info for the rest of us: go ahead & temporarily test-hook that b- up to the stock temp sensor & see what it tells you. If it works, you could always tie the stock gauge's wiring back inline with the Autometer's.

BUT: If the broken-off Autometer sender is able to be removed from the block, definitely put the replacement sender in it's place, & forget about it. Ignorance is bliss.
-W-