It appears that these part numbers have been superseded once again!!
AC Delco #10-5030, GM #89021182 is now 10-5073, GM #19329448 (32 oz)
AC Delco #10-5031, GM #89021185 is now 10-5074 (I don't know the GM#) (16 oz)
I ordered the 10-5030 from Amazon and they sent 10-5073. I needed more for a flush, so I checked out Pep Boys. They had the old stock behind the new stock on the shelf. The labels on the 10-5030 & 10-5031 look older and are yellowed, while the labels on the newer numbers look new and pristine (not yellowed).
From this I can safely conclude that these are updated part numbers, not differently spec'd fluids. Possible change in manufacturer? The bottles are the same design, MSDS # is different, though.
When ordering from Amazon, ordering by AC Delco number will give a different price than using the GM number. Always look for all possible numbers for the best price.