[Benzito]

To put a proper finish to this story:

1. Remember that I stuck the Optima back in last week after it worked in my other car and the other battery worked in the Cobra.

2. One last menacing glare and curse of the car on Saturday before I break down and call a mechanic or a tow.

3. I stick my key in and there it goes, like NOTHING EVER HAPPENED. Lights work, car drives, no issues. Battery continues to peg the meter with a full charge. I am happy and I am not looking back!

4. To be safe, I took others' advice and replaced the battery-to-earth cable with an extra on hand. The end that grounds to the frame was cracked a little bit, but was still mounted and had good contact with the frame, so I'm thinking the mount wasn't (fully) the culprit. I hadn't checked it that closely before and didn't fiddle around with it in between the switch in batteries, but better safe than sorry.

I think I just have a bit of Stephen King's "Christine" DNA with my cars. Almost the same thing happened with my other British car (RR County) a few months back when it would crank and crank, but never fire. Three days after I told my wife that I hated the car and I would sell it, it starts up again. Has operated without incident ever since.