What is correct for 1971 GS Windshield Washer fluid lid?

I've seen several early 71's with the 70 style lid. (tube is connected to a vertical center hole). Just last week I asked about a very original appearing 71 GS455 that had this same lid and the car was built in March of 71. When did they switch over to the side hole in Flint?
Thanks for all your help!
Troy
PS, my car is a Feb of 71 build

 

Mine is a late Jan '71 build and came with the vertical hole cap.

 

So we have a January and a March example with the 70 vertical hole cap.
I'm looking for a nice 70 vertical hole cap if anyone has one.
Troy

 

Here's a picture of a late April 71 build with the vertical hole cap.

 

Ken and Brian, thank you very much for the input!!!
Just one follow-up. Are these Flint built cars?
Troy

 

Hey Troy. Yes, Flint built.

 

I see them with Stepco written on the tab in both a large and small font? Could that differentiate earlier and later style?

 

The 90 degree or horizontal outlet w/w/cap 3798372 was used on all Buicks and Chevrolets in the mid to late 60’s. In Nov/68 Buick stated that all Buicks used 3798372 and/or newly introduced part with vertical outlet 1231266. By Oct/69 all GS/Skylarks used 1231266.
All three build manuals, ’70, ’71 & ’72 show this cap 1231266 being used and so noted on Build Illustration dated Dec/68 for the 70 model. Jan/70 for the 71 model and Jan/71 for the 72 model. It can also be seen on Illustration dated Jan.27,1971 that the horizontal cap 3798372 is to be used on B,C & E bodied cars.
History timeline shows:

3798372 – 1231266 as of Oct/69

1231266 – 470994 which has cast part usage on top of cap, Model usage ALL car lines, Jan/82

470994 – 25500278 which has the same cast but with white lettering, mid 80’s and model usage is ALL car lines.

The vertical outlet 1231266, Buick states that by May/72 ALL Buick models used this cap also as a factory replacement.
If the horizontal cap 3782372 is on your totally unrestored 71 or 72 GS then in my opinion it was a factory assembly line error. OR possibly replaced sometime in the cars early history.

Manufacturing source for all is STEPCO.

 

I've noticed the difference in the past, but because the vertical outlet being correct for these cars I didn't think twice about it.

The only time GM / Buick changes a part number is when there is a design change or manufacturing source change. The vertical outlet
cap 1231266 change apparently was by the source or by request from GM for larger ID recognition.

Therefore no design change, no part number change. But I agree on early and late style.

1st pic cap off 72.

 

Well...all I can say is I learn something new about these cars everyday.


GM / Buick illustration dated Jan. 27, 1971 for the ’72 GS/ Skylark indicates

That the vertical outlet 1231266 cap was to be installed from the factory.

That same illustration had a revision update, dated April 19, 1971 indicating

The 3798372 cap with the 90 degree outlet was to be installed on the ‘72 model instead.

And what I still find interesting is within a year the 1231266 cap was the replacement cap for all models of 1970 – 1972.

My apologies for the mis-information.

 

This is such great detail and information to answer my question.
David W also shared with me, for those of you that own a 70-71, and need a new Stepco W/W cap, Ames Performance has a nice reproduction and the part number is P191M.
Troy