I run two group 24 marine RV batteries Costco brand and a 100 amp one wire alternator, no issues starting my S/P 508 C.I. 15.2 to 1 E 85 motor
high amp draw electric water pump, BG 400 electric fuel pump, fan, MSD7AL and so on.
I will charge them every now and then during the winter for several days at 3 amps and sometimes between races if I haven't race the car in the last 2 or 3 months just to make sure they are top off
They are around 6 years old so I may end up replacing them soon if they don't read at least 12.5+ volts after sitting for several months. They will read 12.65 after charging and sitting several days after using the car the last time I check them
I have a voltmeter in the car that shows the battery voltage any time the ignition is on, it will read 12. 3 + volts not running and 14+ volts when running with everything turned on and running