What was the original battery group size for the '74-'78 C-Bodies?

[1978 NYB]

What is the original battery group size for the '74-'78 C-Bodies? Was an optional heavy duty battery available?

 

[commando1]

What is the original battery group size for the '74-'78 C-Bodies? Was an optional heavy duty battery available?

Group 27.

It's not the group number that differentiated the batteries.
It was the cranking hours (# of lead plates) inside the battery.
The 74-78 C's used several types depending on engine and options.
The heaviest battery was on the 440's with 100A alternator but I don't know about the cop cars.
If you get a Group 27 w/650+ crank amps, that's about as high as you could have got back then anyway.