Lead acid batteries don't make much sense in 2015, and originality makes as much sense for batteries as it does for tires.
If you don't want to mess with fitment, get the same size/shape. If you think you'll lose sleep over it, get the same CCA rating as the stock battery. There is, however, room to optimize:
Aftermarket Car Batteries For Your Honda - Battery Science - Honda Tuning Magazine
Some take-aways from this random Internet article:
- CCA only matters if you expect to start your car at 0°F. If you never start your car when it's below freezing, you can go by the much more forgiving MCA in a battery half the size.
- If you don't listen to the radio with the car off regularly, and there are no other electronic gizmos that drain it, reserve capacity doesn't mean much either.
- Battery life has very little to do with sizes and brands and very much to do with how you treat the battery. If you put a charger on it every time you park it, your battery will last a long time. I just pulled a battery out of my '84 911 from 2006 (though I've never had a battery go this long).
For my next battery purchase in that no-gizmos fair-weather car, I plan to get an AGM battery with less than half the rated cranking power as stock. I'll let you know if it turns out to be a horrible mistake.
I had no idea '69s had two batteries, that's neat!