In Commodores, the change was during the VC in 1980 - both the 6 & V8 were upgraded with the bigger bearings.
Around the same time the power steering pumps went metric too.
I had a March '80 VC 253 with the short pump & imperial p/s pump, and an August '80 308 SL/E with the long one & metric p/s pump.
This was back in the early 90s, when you could easily source both types of pump, and both cars were likely to still have their original water pumps - hence I doubt they would have been changed, as there's too much else to change over at the same time, so you'd buy the right pump rather than stuff around.
I initially thought it was an A/C or no A/C difference, as the 253 had no air, but then found many others that debunked that idea.
I'm not sure when in 1980 the WB was released, but that's another thought that I had for a while. I spent ages looking through parts manuals to try & find the changeover point, but it wasn't real clear - just listing long & short types for the pumps & fan spacers.
Going off my engine numbers list, which those 2 cars are on, it's somewhere between VR114xxx and VT148xxx.
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