64 rear carburetor is a different part number and has a different setup on it for the kickdown linkage (64 ST400 trans had a switch that the throttle arm came back and hit at full throttle--did not have a link attached to the throttle arm like the 65 and 66 did). Since your car is a manual transmission, that does not matter unless you are looking to have all correct 65 stuff on there. 65 and 66 are identical other than color of the paint on intake, which can easily be changed. 66 aluminum valve cover on pass side has the pcv valve angled for better valve cover clearance, whereas 65 and older ones have it sitting straight up and down. 66 Drivers side aluminum valve cover has a big divot in the front corner of it to clear the california AIR system pump that was on the cars sold in CA. So unless you can't find anything else, I don't recommend the 66 valve covers on a 65 since they stick out like a sore thumb to people familiar with these cars.
