They're oil pressure sending units. If I remember correctly the one on the left is for a full variable gauge and the one on the right is for a dummy light.

 

Thats what I thought too..

I just took the cluster and sending unit out of an auto 95 4runner 4wd v6 and that's the sending unit it had..

I swapped both over to my manual 93 pickup 4wd 22re, plugged in my connector to the 4runner sending unit and the gauge seems to be working correctly...

 

disagree.

The left is a factory style sending unit, the right is not a factory style (but still probably a sending unit, you can tell the two apart typically by size of the diaphragm) maybe not even Toyota I don't recognize the plug but I've certainly not seen them all.

A "sending unit" implies a variable resistance output, not to be confused with a "switch" which is either open or closed.

 

They’re both sending units for a oil pressure gauge, not a light. The one on the right is for slightly newer vehicles. Probably the only difference is just a more positive lock of the connector.