discharge/overcharge?

the title says it even though it sounds stupid. im getting confused on what should be a simple system. anyway here goes and any help is greatly appreciated. was out driving the car the other day and noticed that the amp gauge was showing a slight discharge, it usually reads a slight charge or not at all depending on its mood I reckon. anyway I stopped and went into a store and came out and restarted, it started fine but showed even further discharge. I had to make another stop and when I was ready to go home it was close to dark, had to turn on the headlights, with the headlights on it showed a serious discharge but all the lights were nice and bright and it started up with no problem so I headed home, drove probably less than a mile and the car just shut down, lost all electrical, lights ign everything. had to have it dragged home and stuck it in the garage. started cking it this morning and found that one of the previous owners had installed a "fuse" holder in the red wire coming from the starter relay to the amp gauge, i'm assuming in place of the fuseable link but its right at the bulkhead connector. it had a 20 amp fuse in it that was blown. replaced the fuse and it fired right up, put a meter on it and its overcharging, fluctuates a little but basically 15.5V with the headlamps on but the amp gauge still shows the serious discharge. idk, I started checking and looking at posts but im getting confused I suppose. I cant seem to locate a service manual with charging system trouble shooting if I could im sure I could get it figured out, anyway here's what ive done. im getting battery voltage to the B terminal on the alt, when its running the voltage at the battery and the B terminal match. I unplugged the green field wire and it quits charging, plugged it back up goes back to 15.5V. I added an extra external ground to the voltage regulator, no help, I put another regulator on it (already had it , should be good but who knows right but what are the odds of them both being bad and doing the same thing) anyway no help, if I unplug the voltage regulator and ck the voltage it shows about a volt less than battery voltage running or not running on both wires, if I backprobe it it shows about a volt less than battery volt on the "I" wire and approx. 6 volts on the "F" wire (idk if that's right or not). i cked the connection at the amp gauge and it was tight, i unhooked those and connected them together with a nut and bolt just to bypass the gauge and still no help. looking at the wiring diagram on a mad link i found it shows the voltage running from the alt on the black wire to the amp gauge and then back to the batt, if i unhook the amp gauge i don't have any voltage on the black wire, only the red wire and if i unhook the black and red wires from each other (the ones that are for the amp gauge) to check for voltage on the black wire with the car running it kills all power and the car dies like it did the other night so that diagram is confusing to me. im sure im overlooking something and ive read so many posts and looked at the wiring diagrams so many times im confusing myself. i also found a simplified picture of the charging circuit and followed all of that out and all seems to be connected correctly. i do loose that volt from battery voltage like i spoke of earlier at the volt gauge and ign switch connector but they are still about 14.5v with the car running so its still seeing the overcharge in there. the bulkhead connector obviously is old and not the greatest but doesn't seem to terrible but is dropping that volt going inside, not sure if that can cause my issue but it is showing overcharge at the amp gauge and ign switch connector but shows discharge on the amp gauge itself when hooked up. so sorry for the ramble, i was trying to give all the info i had. i did stick another alt that i had laying around on it but still no help. any suggestions? anyone have a link to a service manual where i can follow diag? thanks again.