One other thing, golf cart batteries IIRC are designed to be discharged
a bit more deeply than are regular deep cycle batteries. Running a
golf cart around a course all day is pretty taxing work for a battery.
You'll probably get far more usable power out of the golf cart
batteries than you did out of the 8D. And if you have a cell fail, as
you did in the 8D, you won't have to spend as much to replace it. I do
generally recommend that the batteries in a bank be the same age and
make, but if you kill a cell, swapping in a newer battery of the same
make is often doable.