I wish I could get ambitious enough to try that out. I have 2 deceased red caps and a never used yellow cap I'd had stashed for years I came to find had a dead cell when I finally added acid to it and charged it.
On one of my cars which is a local show/driver quality car I finally gave up and put a red cap topper on a group 24 parts store battery and it actually looks pretty good.
I did get a call from Antique Auto Battery this morning, so they apparently aren't out of business.