Year One sells a OEM looking voltage regulator that has electronic internals for $36.
That may help, but your starting problem is probably bad battery cables or grounds. You could also try the diode trick across the ballast resistor.

Someone here in the parts for sale section sells on oe appearing one w a black case and electronic internals for $25 to your door and I understand the some regs can handle more current??and not needed in your app here but I understand you can replace the grounded brush on one of the 69 earlier alts w a insulated brush holder from a 70 up alt to make an isolated field (later type) alt if you ever wanted to use an an earlier alt w a later type 70 up flat VR.

As I stated on an earier post teh dual field thing is misunderstood and they both have dual fields burt the early alternator has one grounded internally. To use a later (70) up alternator with the older style regulator is to ground one of the field terminals either to the case or with a short jumper to any good ground.

If we are being picky, Really, both only have one field.

An electro magnetic field is like anything else elctrical. It needs power, and ground.

On the old ones, the power is regulated, and the ground is constant through the case of the alternator.

On the newer ones, the power is key on battery voltage, and the ground is regulated through the second wire.

Yes, grounding the second terminal completes the circuit when running a newer alt, with an older style reg.

With the new elec reg that looks oe you dont need to cut or change wires.My kids has been in for at least 10 years and charges like a new car.The race reg was meant for that application.Not street.If they wanted a constant charge they could have built it that way and probally would be cheaper.Battery only wants so much charge.Thats why the reg shuts down when its charged fully.Unless you only drive a few miles sooner or later it will shorten the battery.I run 1 gauge cables.Ive seen a lot of older cars that have corossion in the cables that you cant see that cause hard cranking.Rocky

It's a dual field connection, which got shortened to dual field in usage.

Difference between the old and new style regulator boils down to this. The old style regulator switched the voltage to the alternator, turning the charging on and off.

The new style varies the ground and can control the output in a smoother manner.

Temperature compensation was built into the OEM regulators, the MP constant output one does not compensate for temperature, which is the ONLY difference. Might it shorten battery life? Maybe, I ran one for years and my battery lasted for 8 years with one. YMMV.

So now we have the regulator as thermostat. OK fine if you say so. ---- go ahead and use your cnstant, regulator. Electricity is charge does create heat, heat is what damages the system including the battery and alternator. Using a regulator controls this electricla flow.
http://www.autoshop101.com/trainmodules/alternator/alt131.html
The regulator will attempt to maintain a pre-determined charging system voltage level.

When charging system voltage falls below this point, the regulator will increase the field current, thus strengthening the magnetic field, which results in an increase of alternator output.

When charging system voltage raises above this point, the regulator will decrease field current , thus weakening the magnetic field, and results in a decrease of alternator output.
Also - http://www.familycar.com/Classroom/charging.htm
The voltage regulator can be mounted inside or outside of the alternator housing. If the regulator is mounted outside (common on some Ford products) there will be a wiring harness connecting it to the alternator.

The voltage regulator controls the field current applied to the spinning rotor inside the alternator. When there is no current applied to the field, there is no voltage produced from the alternator. When voltage drops below 13.5 volts, the regulator will apply current to the field and the alternator will start charging. When the voltage exceeds 14.5 volts, the regulator will stop supplying voltage to the field and the alternator will stop charging. This is how voltage output from the alternator is regulated. Amperage or current is regulated by the state of charge of the battery. When the battery is weak, the electromotive force (voltage) is not strong enough to hold back the current from the alternator trying to recharge the battery. As the battery reaches a state of full charge, the electromotive force becomes strong enough to oppose the current flow from the alternator, the amperage output from the alternator will drop to close to zero, while the voltage will remain at 13.5 to 14.5. When more electrical power is used, the electromotive force will reduce and alternator amperage will increase. It is extremely important that when alternator efficiency is checked, both voltage and amperage outputs are checked. Each alternator has a rated amperage output depending on the electrical requirements of the vehicle. About the same as hooking up and forgetting a constant, non voltage controlled battery charger of past years. Wouldn't think of doing that - would you?

There's a very hundred Mopars around here all useing the constant output regulator. Nobody has any complaints. Mine runs better with it more voltage to coil. I use a .8 ohm resistor. My local speed shop has been putting the constant out regulators in every electronic conversion since they came out. I've used them for years. Never had a problem. Never killed a battery. I'll stick with what i know works from my experience not what i read in the lastest issuse of hot rod mag.