The one on the left is the correct Cleveland t-stat with the hat. That is likely a part of your overheating problem as tweh Windsor oen allows coolant to by pass in the block.
The second part of your problem sounds like the second fan is not coming on. Probably either a bad fan/wiring, the thermostatic switch in the radiator or the relay. You couldl always bypass it to the first fan to see if both run that way, if so it's most likey the thermostatic switch.
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