I have the exact same issue. My original sender says KS with a circle around it and 2. Must be a King Seeley #2. It reads 12.93 kOhms cold and then the resistance drops as it gets hot. I ordered a new sender from KW and it's the same thing. They were super cool and refunded me when I called to tell them it wasn't the correct application! So, I too am looking for the correct sender that starts with little resistance and gains resistance as it heats up. I checked the gauge operation prior to ordering the sender and it functions as you explained and as I've read they should. Full hot key off, full cold key on engine cold then gradually moves toward hot as engine heats up. Mine is full hot key off, full hot key on and then moves from hot to cold as engine heats up.
Please let me know if you found something that worked for you!
Bill