"KS" = King-Seeley, a major supplier of temperature gauges and related equipment. I don't recall the build date of your car, so can't comment on whether an L4 or M4 coded sender would be appropriate, but I'm guessing probably yes.
Dan! You amaces me. Where did you round up all your knowledge? Thanks for the input. My car was assembled in January 27, 1965. Thats why I thought the factory unit from November and my NOS one from December would be ok. I have found parts from week 2 on my car which is pretty close to build date.