Alternator problem..?
 

So, here's the story.
I got a new high-amp alternator, and must not have connected it correctly, because within a day or so, my battery was dead. I put the old alternator back on, and completely recharged the battery, and within a few hours, I barely made it home with any lights on (11 miles). Must've fried the battery or something, BatteryPlus agreed.
So, I got a new battery, which was expensive, but I wanted a new battery soon anyways, and this is a really good one.
Anyways, A new problem is popping up. When I idle, and turn my "fog" lights on (just two utility lights on my bumper), everything is fine. But when I have it above idle, and I switch them on, my radio shuts off, and my gauge lights dim. Did I not re-wire the original alternator right? I accidentally lost the original connector, and had to buy a new one, and there aren't any labels on the new connector. Here's how I wired it, below.
This is on a 350 with external voltage regulator (also new), '1964 GMC.
Blue and yellow wire coming from the loom, new added connector, not sure if it's wired correctly.
Thank you!

Re: Alternator problem..?
 

From what I can gather you have replaced the original alternator with another externally regulated higher amperage version. It would have been much better to get a 12 SI model internal regulated one or a CS version modern style and eliminated the external regulator.

Here is the original 64 wiring of the regulator and the alternator with the engine compartment wiring for added benefit. I see you say the wires from the loom are blue and yellow. The original wires were blue and white so make sure that the blue and yellow wire come from the voltage regulator to the alternator from and to the correct terminals. They probably do since it was charging on the old alternator and the yellow wire is probably replacing the white one.

Attachment 945402

Here is a crop of the diagram for better visibility
Attachment 945403

Notice that the white wire from the regulator goes to "R" and the blue wire goes to "F". Make sure the regulator and the alternator are grounded and grounded to each other.