about 5 years ago, i installed 2ea 6v gpl-6ct lifeline agm batteries from bd batteries online.
they are so tall that i had to install them on their sides in my stairwell battery compartment.
i went from about 190 ah battery capacity to 300 ah battery capacity. they weigh 90# each.
the only problem was that lifeline batteries are very expensive.
a very nice advantage is that lifelines never need water and there is absolutely no corrosion.
my batteries are still performing very well.