Freight cars for my roster

Yes you're pretty much correct, most AZL cards are post-1965. Of their offerings, I can suggest the AAR boxcar. I know that the WP prototype was still running in the 1960s and there is a NH card. The outside braced boxcar is another possibility, although a bit old for the 1960s.

Thanks, I have already the NH AAR Boxcar or a very similar version ... by MTL !. The (Reading) outside braced boxcar is interesting, one 2-bay and one 3-bay hopper (to be mixed with other cars and unloaded in a station "outside" the layout) would be a good choice (GN ? CN ? ) ; the LPG tank cars are too long ; I have already 2 gondolas (Reading, and NYC via the Bay) by MTL, and unfortunately there is no caboose for NH or NYC.

Needtrains.com has 2-Bay hoppers for NH

PS2-cd date back to 1963. History: Valued for its large capacity, roof trough hatches, and center discharge gates, the 4427 PS-2 CD High-Side Covered Hopper was a favorite for hauling grain. These large hoppers could be found across the continent hauling grain and other medium-density loads beginning in the 1960s, often in multi-car cuts or unit trains. Many are still seen in service during the fall harvest, 30 years after their construction.

Even with Pullman Standard Car Manufacturing Company's passenger car designs and patents spun off to a separate company called Pullman Technology in 1982 (which was eventually sold to Canadian based Bombardier in 1987) and Pullman Standard's remaining railcar manufacturing plants and freight car designs and patents sold to Trinity Industries in 1984, American manufactured Pullman freight and passenger cars were (and to this point in time still are) well known in North America.

When it came to hauling dry bulk goods such as agricultural commodities, cement, clay, dry chemicals, salt, or sand. many railroads and private owners selected the Pullman Standard PS-2 series covered hopper.
Utilized to transport dense and heavy granular products like cement, clay, potash, and sand, due to North American axle weight load limits, two (and later) three bay models were often chosen.
When it came to hauling much lighter commodities such as barley, corn, grain, malt, oats, soybeans, sugar, and wheat, these kinds of products would most commonly be transported in three or four bay covered hoppers.
Unlike two bay models, large four bay cars lend themselves to rapid load and discharge operations.

While there are a wide range of products covered by the PS-2 designation, it was Pullman's 4427 cubic foot capacity covered hopper that stood out as being the first of the larger capacity models to be manufactured in greater numbers.
Introduced as the PS-2CD (center discharge) in late 1963, the early production "low hip" design 4427 cubic foot capacity cars had low body sides, which concealed most of the hopper bay area.
The manufacturing of "high hip" design raised side 4427 models commenced in November 1966.
Over 19,300 PS2-CD 4,427 cars were produced.

Visibly apparent are a few different body style variations.
With the latter style being the most popular choice, the top of the covered hoppers could be fitted with large trough style openings, or, a series of round ones.
With the latter position being most common, brake wheels could be positioned high up on the body end, or, low mounted.

The 4427 is a very different animal than the 4750's. I stand by my contention that the 4750's would be an anachronism. However, in Z I am ok with a few of those...will have some anachronisms on my pike too. I just wouldn't have a unit train of them or something like that...but a CB&Q scattered in here or there would probably make the cut for me too. (again, anybody can run whatever they want as far as I care, but if you're asking the question about what is appropriate for a certain date, then that's my answer.)

I plan to have a few of the AZL LPG cars on my 2005-era railroad...they were very rare bordering on extinct at that point. Most of the ACF's AZL does had been replaced with newer bigger models by then too. But, we deal with what is available to get some variety.

From some previous research I was thinking late 70's/early 80's for the pink cars, and the reference I found quickly online was early 80's so I would feel pretty good about the accuracy of that.

I think most of the Co-op cars will be the same timeframe.    Not saying that 100% but that's a pretty big project to track all those down.   Your best bet is the CB&Q, GN, and possibly the non-shield UP cars.   That's just a guess....start getting too far prior to 1980 and my breadth and depth of knowlege tapers considerably, and I don't claim to be an expert in any era.  (anything mid/late 80's to late 2000's is my strength, for what it's worth.)

Sorry forgot about that part of your question.   I  can measure one of the AZL's when I get home from work, but the prototype cars are 60ft.