What would be the correct San Jose radiator for a 200 engine and C4 trans. Which numbers would need to be on top if the Mustang was manufactured January 1966. Would like to find a radiator from Oct-Dec 1965
The radiator based on the study would have W-MO and the date stamped in the top tank and a ID tag applied to the passenger side radiator strap. Looking at other 6 cylinder automatic examples without AC or thermactor (just guessing on the last two since you didn't mention them) I found of C6ZE-A2. Picture of that ID tag is shown in the Unrestored Picture thread.
Unfortunately this example is from a possible June 66 built car so can't be certain the coding was the same 6 months or so earlier but nothing I've seen so far shows that the ID number changed for applications during 66 production.Not as much research has been done on 6 cylinder cars, a fact that I'm sure you have discovered. In turn less examples and pictures out there. Note that there are some decade old list of ID codes roaming around. IMHO not all are completely accurate and I would not rely on them solely