Ford used the 27F and the 24F, Mopar the 27 and 24.
Top post GM batteries were 22F, 24 and 24T(tall 24), AKA Delco Y55, R59, R69.
The 27 isn't hard to find, it's the 27F that's not as common.

I've been using a 27F as a replacement for the 31 that came in my tractor. Last week, the Walmart 27F that I had in it died, so I went to get another. Neither Waldoworld or Sams Club had a 27F, only 27's. My cables are just long enough I could get by with a 27 so I bought a Duracell 27 from Sams. Cost was $101+tax.
If I couldn't have been able to make the 27 work, I was going to use the Duracell 24F. The reason I was going to try the smaller 24 is the Duracell 24 has a CCA rating higher than many 27's of other brands.

Go with a good group 24 and forget the heavier 27, it will start a 451, especially if you have a modern starter.

If you think all Walmart or other box store batteries are inferior, I've used Walmarts batteries for 25 years. Most last 50% longer than the warranty period. The best one I had was in my '68 V200. Bought it in 2001, it died last summer, 15 year life span.