Look you need to FIND THE PROBLEM that is causing this before you go around assuming that an internal or one wire is going to "fix" something.
Internal, by the way, and "one wire" are two different things. There are / were many alternators that are / were made with internal regulators, which are not "one wire."
There IS a DIS advantage to using a "one wire" "sometimes."
For one the "sensing" is generally right there at the alternator output terminal. This means that if the charging wire is too small OR IF THERE IS A PROBLEM in the output circuit, the battery voltage will be low, or MAY BOUNCE AROUND
Start by reading this article:
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
If you do not have one, go over to MyMopar and download a factory shop manual
http://www.mymopar.com/index.php?pid=31
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I tend to think of charging problems in several SECTIONS
The alternator
The regulator
The field wiring circuit
The alternator output circuit
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"Some stuff." If you have not checked voltage RIGHT AT the battery, the charging system might not even be your problem. Might be loose connections inside the passenger compartment
Some other possibilities:
Loose / damaged / corroded connections in the bulkhead (firewall) connector. That is largely what the MAD article above is all about
"Other" loose connections, including right at the alternator
Worn brushes or other internal problems in the alternator
Bad connections in the field wiring, including the connections right at the VR, and (again) the bulkhead connector.
Something wrong in the ammeter. This is somewhat more rare, but does happen, and is addressed in the Mad article
Redfish (member here) has mentioned the following many times. The later cars have a white plastic connector up above the engine near the firewall, connecting the engine harness to the rest of the underhood harness. These are TROUBLE.