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Ryan,

The search feature can help you find dozens of threads describing your exact problem, so if somebody doesn't answer right away, you can still make progress.

First of all, if the battery only measures 11.98v, it needs to be replaced. Put it on the battery charger for THREE DAYS nonstop, if it doesn't measure 12.6 volts or better, it's junk.

Second: 1968 911s had a Bosch 35A alternator and Bosch voltage regulator. 1970 911Ts used a Motorola 55A alternator. You are always supposed to use the same make of regulator and alternator according to the factory. So, get yourself a Motorola regulator, or something aftermarket that is adjustable like a Transpo, so you can set the output voltage yourself. You are clearly handy enough to use a voltmeter so this should be simple The problem with mixing brands is that the "set-point" for DF voltage is different based on the input voltage. Probably not a HUGE deal but a good idea if this is intended to be a long term fix.

I would NOT mess around with full fielding the alternator, you will probably just fry something.

You don't need to measure the voltage levels on the various components, that's making it too hard. Since you know the bulb works and you know you have +12V on the blue/yellow side of the bulb holder on the igntion switch, simply do the following:

1) Disconnect the blue wire at the bulb holder. Using a jumper, measure the resistance in the blue wire from the bulb holder terminal back to the D+/61 terminal on the voltage regulator. Should be close to zero ohms, anything more is a high-resistance connection somewhere.

2) Measure resistance from the blue wire at the alternator (without it connected) back to the VR. That should also be zero.

3) For a final check, with the ignition on, ground the blue wire that connects to the alternator D+/61 to ground. The bulb should glow brightly. DO NOT LET THE B+ TERMINAL TOUCH GROUND IF THE ALTERNATOR IS OUT OF THE CAR, YOU CAN KILL YOURSELF OR BURN THE CAR DOWN.

Now you know you have continuity in the blue wire. After that it's either a bad VR or the alternator. Since the alt is new, I would suspect the VR.

Report back here with your results and I'll give you more advice. Good luck!