Yep need to know mor einfo.. does she actually have a bad battery and spin slow.. does she have wimpy 4ga automotive bat cables designed for 12v.. vs the beefy 00 cables that 6v needs.
is the battery good? terminals clean? good ground to the steering box ( not the battery box ).
clean correctly gapped points? good non fouled plugs?
got good compression?
fuel system in good health?
soundguy