The regulator you pictured is NOT a mechanical regulator. It is in fact a solid state regulator similar to the NAPA/ Standard transistorized regulator.
THE REGULATOR on your car now may very well NOT be at fault.
NO!!! the green wire is NOT a ground, that is your field wire connection. The regulator MUST be well grounded to the mounting flange. If there is any question, run a separate no 10 wire from the engine block or the battery NEG to one of the mounting bolts.
Run some tests to check for dimming there are SEVERAL AREAS of concern
1---The supply voltage (ignition supply, the blue wire) may have voltage drop. To check this, hook everything up normal. IF you have breaker points ignition, make sure the points are CLOSED. To do that, hook your meter from the coil NEG (distributor side) to ground, and turn the key to run, engine OFF. If you measure battery voltage, the points are open. Bump the engine until the voltage goes very low.
NOW to make this test, key on, points closed, engine off, hook one meter probe to battery positive, or the starter relay battery stud. Hook the other meter to the blue connector on the regulator. Leave the blue hooked up, just "back probe" the connection. You are HOPING for a very LOW voltage reading, the lower the better. Anything over .3V (three tenths of a volt) means you have a drop proplem in the ignition harness.
The circuit path in question is the battery -- fuse link-- through the bulkhead connector -- the ammeter circuit -- the welded splice -- the ignition switch connector -- through the switch -- back out the switch connector -- back out the bulkhead connector (on the dark blue ignition lead) and finally to the regulator and ignition system.
SEVERAL places in this path can have a bad/ damaged connection and cause a voltage drop, and your top suspect is the bulkhead connector.
2--the regulator may not be grounded To check this out, run the engine at an RPM to simulate "low to medium cruise." Stab one meter probe on the battery NEG post, and the other probe directly onto the mounting flange of the regulator. Be sure to stab through any chrome, rust, paint. As before, the lower the voltage, the better. Zero is perfect
3--There may be voltage drop in the charging wire To check this out, get the engine running as above, and turn on all accessories you can, radio, heater blower, lights, etc.
Put one meter probe on the battery POS post (or the starter relay battery stud) and the other probe on the alternator output stud. Here again, the lower the reading the better. If you see anything approaching or more than a volt, you have a voltage drop problem, either in the bulkhead connector, or the ammeter itself.
4--It may be a "combo" of alternator problems---worn brushes, one bad diode, a low output alternator with added accesories, or just the fact that you have an early style alternator. The later so called "square back" alternators are much better, and can be used simply by grounding one of the second field connections
That is, your present alternator should have one permanently grounded brush. You can buy a later squareback, and add a jumper wire to the second brush, and just bolt it right up
An older roundback. This one is a "rebuilders trick" The original grounded (69/ earlier) brush is at left, and the original insulated brush is at 12 o'clock. the circled hole is one a rebuilder has drilled to install an insulated brush so that this earlier alternator can be sold for use on a 70/ later "isolated field" system
Later "squareback" far superior at low RPM charging. You can use this with your regulator by grounding either brush and hooking your green field wire to the other. On some of these, you can pick one or two small washers, replace the fiber insulator, and ground them without making a jumper wire.
5--In some cases the battery may be a factor as well, IE too small, or on it's last "days."
PLEASE read this MAD article which points up some of the problems with Mopar wiring and the bulkhead connector:
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
6--Last, much of your lighting problem my be that you need to upgrade the headlight wiring and install headlight relays There are several areas of concern here, too:
6A--It doesn't help that the headlight sealed beams may be old THEY DO get dimmer with age
6B--The grounding and lamp connectors may be deteriorated. Replace them and clean up the grounds
6C--You may be getting voltage drop in the headlight supply circuit. Here again, our old friend the bulkhead connector is no 1 suspect, but you can lose a little here and there along the way---
loss in the main charging line/ bulkhead connections
loss at the headlight switch connector and or the switch
loss at the dimmer switch connecor and or in the switch
loss at the headlight high and low beam terminals in the bulkhead connector
The answer? HEADLIGHT RELAYS
