Sudden loss of battery power to starter after changing batte

I just completed a restoration on a 1952 FARMALL Super C along with adding an old loader I found rotting into the ground and picked up, reinforced sand blasted painted re reinforced some more and have it ready to paint. I also Fabbed up a front blade from an old John Deer. It's not the prettiest but very functional and fits on the loader. I had a tired battery in it that would go flat in cold weather and here in Michigan that's not good. I just pulled it and got a new battery and put it in and without thinking hooked the neg. Ground up(converted to 12 volt) and while putting on the pos term, lghtly sparked it on the pull starter rod. No problem, seen it happen many times with just someone jumping a little and feeling stupid. But this time after hooking everything up I was only getting 7.7 volts to the starter bolt even though battery read 13.3. Also I put charger on it for several hours and when I came back the light on the charger was blinking a fault. Checked all wiring and redid wire from amp meter to switch that was not looking good everything checked out with wiring but still nothing. Changed starters and put in one from standard 1938 C, nothing....took jumpers and went from battery to starter bolt got 13.3 volts but still nothing when pulling starter/engaging starter bolt. I know this kind of thing is not easy if your not here seeing it but I'm hoping someone else has had this happen and can give me advise.

Thank you,
M. Conely