Here's a l'il sumpin for ya. You said it sat a while. I'd bet an old tin valve cover your armature has a skin of surface rust on it. Had the same issue with a 33 flatty last year. New battery, cables, starter switch, same ****. I pulled the starter and it was covered in that ugly flash rust look. I cleaned it up real nice with a red scotchbrite pad, sparyed a bit of WD on it and slapped it back together. Turned over damn near like 12V. Cost: some time and a few cuss words. Just a thought before you piss away $500 bucks on batteries.
I had similar problems with my stock 47 Ford with a single 6 volt Optima battery. The cure was the grounds. I cleaned the stock body to battery ground and the stock body to engine ground, then added a direct battery to engine ground. I added star washers on both sides of the ground cable connections. That fixed all my problems.
what is the trick to removing a starter on a stock 53 lincoln . it hits the cross member and no matter how i twist it , it won't come out .