did you come up with anything yet? no one else has chimed in so i'll throw 2 Bob in
as near as i can tell early built 65's (that is mustangs built in 64) used a twist on lid, white logo. one parts source (US) says twist lids were before 3/9/64 (!) but i thought i had seen them on much later
, perhaps he meant before sept 64 or march in 65 (?) . then its the not wide bag, white FOMoCo script with flip top for 65's and most 66's. it appears late 66's (think i saw the month Oct when i was reading something, at that month i cant imagine many 66 got them!) may have used the gold script wide bag which was used on the 67's until they changed to plastic reservoir after march in 67.
of course there can be some overlap and some bags (reservoirs) from other ford models fit so you could end up with anything from red wide bag (e.g. from a 66 galaxy) etc if it was replaced or added for any reason. or in 65 if the car wasnt ordered with the option extra washers you could end up with a red bag that came in a kit the dealer could install, usually had rotunda written on it but i have seen fomoco red bags as well, no doubt you could insist on a black reservoir if you didnt like red because the flacons and comets used them.
