As FID mentioned above, as I'm a Newbie, I was wondering why my 1951 Henry J wasn't "turning over" fast enough. I was paid a visit by 3 members of the K-F Club and one of the first things that was noticed, the previous owner had installed 12 volt cables to the battery. A friend made up larger diameter "aircraft grade" cables....Now the starter spins like crazy. Also, the positive ground cable was "grounded" to the generator bracket. It was rerouted to the block.
So, as I'm finding out, sometime, the simplest fixes correct the problems. Why replace the battery, starter or other parts, when all it could be were the cables.
Reggie