'64 buffalo,
You mention 'voltmeter' several times in your post..do you actually mean ammeter. A voltmeter should hang around 14 volts and not move or jump much. The ammeter will jump around with any schizo activity in the system. The chances of getting two bad batteries is not good!
Chevrolet's are famous for 'clicky' solenoids, so this isn't too strange. A reluctant solenoid won't discharge a battery or cause a drain on the system.
It isn't unheard of for the extra kick of a jumper battery to cause a problematic solenoid to start the rig. It sounds like you have two separate problems.
Does your '64 burb really have a externally regulated alternator? If you replace the starter solenoid, you could focus on what is making the charging system malfunction. The regulator should never allow system voltage to climb above 14.8 TOPS. If the meter in the cab is truly a voltmeter and it is swinging around, the alternator is funky, or the voltage regulator is funky, or the wiring associated with these two devices is loose or broken.
A ammeter that hops around is a lot different than a voltmeter that has the jitters. Do some more digging and keep us posted.
Stuart
