Such charging questions are asked and answered a gazillion times on the A-body forum. 67Dart273 is ever patient there.
Make it simple. Disconnect everything from the 2 field terminals. Using a multimeter, verify that both terminals are isolated from ground. The only difference in 1960's round-back alternators is that one field terminal is bolted to the housing and has no spade lug.
Then, measure resistance between the terminals. I am guessing should be between 10 and 50 ohms. If <1 ohm or >1000 ohm the alternator is bad (field shorted to ground, broken field wires, or bad brushes). But, the factory manual should state proper readings.
Finally, do as suggested by many. Ground one field terminal and apply BAT+ to the other terminal. That will manually force "full output". Do not have any other wires connected (like Vreg) to the fields, but do have the thick output wire connected. It should be a low resistance path thru the bulkhead, dash ammeter, bulkhead, to BAT+, but you can make it direct by running a thick jumper straight to BAT+ (termed "MAD Bypass"). Running the engine, you should see >15 VDC at the cigarette lighter (can buy a little voltmeter that plugs-in, great for monitoring so no charging surprises on long road trips), especially if you rev the engine. Don't turn on any bulbs or things you don't want damaged by over-voltage. If nothing above resting battery voltage (12.6V), verify a good ground connection from the case of the alternator thru engine block to BAT-. That was my problem once. I just needed to sand the alternator case where it bolts to the bracket. If you measure dV > 1V from case to BAT- (engine running), you have a bad ground path.
Don't run too long as above or you will overcharge the battery. Now work on connecting the Vreg. The old typ use "high-side switching". You ground one terminal and it adjusts the other terminal up to 12.6 V to regulate field current, and thus output current. The old electro-mechanical Vreg switches on & off. The new solid-state ones probably switch on-off too, but could adjust proportionally. The 1970's Vreg use "low-side switching". You apply constant 12 V (key-switch) to one field terminal and Vreg connects the other terminal to ground on & off to regulate field current.
For those w/ newer Mopars (say 1985+), they use the same Vreg circuit (low-side switching), but moved it into the PCM. If the Vreg circuit fails, rather than change the whole PCM, many people just intercept the wires and rig in a 1970's Vreg, plus apply a fake "I'm alive" signal to the PCM so it doesn't fuss.
