ok new at this engine stuff, my 78 was missing the sending unit, finally purchased a new one and have the electric connection for the end of the sender but  can't find the screw threads, is it accessible from under the hood or does the car have to be on a lift to access the sender location.

on my 77 the temp sending unit is on the driver side between the front 2 plugs cylender 1 and 3

To elaborate on Raider1's reply, the sender screws into the side of the head, between the spark plugs.  Sometimes there is a pipe plug in the hole that you have to remove.  Be sure to check the same spot on the other head to make sure there isn't an open hole there, too.

Larry

ok sender is next once I get the speedometer back in and see if it works. Thanks

Don't forget you will get anti freeze coming out when you change the sender.

On my 1979 the sending unit is on the drivers side, between Spark plug 1 and 3. same as 77.