TPIMarow6.6

I Got my car running with my 406 and edelbrock heads, the problem iv ran into is that the plugs on the heads are coarse thread and the stock temp sensor is fine thread. and its a little differently shaped. so i put the temp sensor from a 73 caprice 400 in my car but i had to put it in the thermostat housing and i get no reading on my gauge. is there anyway around this or getting the stock temp sensor to work in the car? the old(brand new) 73 400 sensor has a flat tab for the plug and the stock one in my car has a flat circular end on it. but the wire will go on both. so i dont know if its a different ohm reading on the different sensors or what not. so i dont even know if im running hot or not. please if anyone knows anything lend me some advice.