electric fan thermostat location problem

[Kaptain Kadian]

Hello, I am in the middle of swapping out my old radiator with an aluminum one with dual electric fans. The issue I have come into is the threaded port on my new radiator is smaller than the 3/8 threaded temperature sender from my derale 16749 relay kit I bought. I am not positive what size the port is, buy my question is, should I try to find an adapter or find another temperature sender? I have read a lot about where to out the temperature sender and I think I want to leave it in the radiator. I saw where someone put the sender in the return house of the radiator. I don't know if that would be a good option either. Thanks