1987 IROCZ 305FI, want to replace the temp sensor for the gauge. what does the correct sensor look like. current sensor has a pin, but replacements have a tab. ??

 

It's not a "sensor". It is a sending unit, and it threads into the cylinder head on the driver side between cylinders 1 and 3 on V-8 cars.
Yes, all the replacements have a different connector...

 

Is it the Pin type sending unit?

 

AFAIK none of the replacement temp gauge sending units have the factory-style "mushroom" connector. Haven't for decades. No idea why. No idea why the factory used the "mushroom" instead of the more ordinary type, or why there are none in the aftermarket, or where they got them from. After all, regardless of people's hallucinations about AC/Delco being "original", replacement parts don't all come from the same suppliers as OE ones do.

Doesn't matter though; the connector on the wire fits the other style just fine.