I believe a battery tender of at least 4 amps can charge a dead battery and then maintain the charge. Smaller than that all bets are off and you need a proper battery charger to bring it back up.

1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration