I have a Conv D built in November of 1958 that has the thermostatic oil valve engine. Those engines are usually referred to as 1958.5 engines, which means to me that they were built in late 1958. I would think that any cars/engines built after the August factory shutdown would be considered 1959 models. Therefore, many, if not most, of the thermostatic engines would be in 1959 model cars.
To complicate matters my car and many others in many years of production was titled as a 1958 model. The confusion probably arose because in the US October was when all the next year's models came out, while in Europe I think they came out nearer to Jan. 1, if at all (no big yearly design changes like we had here back in the 1950s and 1960s). When I moved to a new state, I was able to change the model year to 1959, as, in my opinion, all Convertible Ds are '59 models even though many were constructed in 1958.
Hope this helps. I'm sure someone will be able to give an engine serial number of the last of the thermostatic oil valve engines. I don't have my books with me here. The factory bulletin recalling those engines would give an approximate date of when the factory pulled the plug on them. Maybe Charlie can pull that one out? I know that by June of 1959 when my coupe was built the thermostatic valve was gone.