I have a 1970 GTO with a 400. The tempeture
sender plug in is for a 3 prong sender.All
I can find is a 1 prong sender. Is there an
adapter for this or is there somewhere I can
get a 3 prng sender?

I have a 1970 GTO with a 400. The tempeture
sender plug in is for a 3 prong sender.All
I can find is a 1 prong sender. Is there an
adapter for this or is there somewhere I can
get a 3 prng sender?

The temp sender on the 70 GTO is a combonation temp sensor and TCS switch (which is why it has three connectors, one is for the temp sender, other two are for the switch). All the parts places "list" the sender for the 70, but all send the same wrong one with single connector.

You can either try and find a NOS correct one (usually $30-$45-or more when they pop up on ebay from time to time) or you can substitute the single lead sensor and leave the TCS disconected (which disables the TCS and will require that you cut the harness and add a single wire connector to plug into the "wrong" sender. The dark green wire is for the temp gauge.

I too had to settle for the 1-prong temperature switch. I no longer have any TCS hardware on the motor so I simply plugged the appropriate terminal of the 3-prong connector to the single blade on the temperature switch.
If you are trying to utilize the original TCS and need the correct 3-prong switch, I have no idea where to obtain them.