On my Group 24, a Duralast battery from AutoZone was the best fit.
The toppers are wider than the '68-'70 B battery hold-downs, though, so you have to either tweak the hold-down or file some clearance on the sides of the topper.
The other benefit of the modern batteries is they don't gas off and create an acidic mess underhood.
It bugs me to not use the correct battery on an original or correctly restored car, but that's better than re-painting the engine compartment.