Electricity is not my friend but I can pass on what I have heard. Sometimes alternators with internal regulators can short out and drain the battery. I don't know how this translates to alternators with external voltage regulators. Perhaps someone else will comment.
What I know to do is remove the positive post from the battery and put an amperage gauge in between the disconnected clamp and the battery post. If all was well, it should read 0 or somewhere real close to it. Yours will probably read quite a bit more since you have something that is draining it. With the gauge in place start to remove the fuses one by one until you see which fuse circuit allows the gauge to show 0. That should be the circuit where you have the drain. Then you have to go from there. Don't forget to unplug the voltage regulator the same way to see what happens. Hope this helps. If anyone else is reading this and I have given incorrect information please make the correction in your post. Good luck. John.
my 73 240 had the same problem after days of looking for
a short i noticed the voltige regulator had been replaced at
one time or another it didnt have the removable cover so i
purchased one for a 73 and it solved my problem
and a friend of mine has a 260 with same problem as you
and come to find out hi alt was shorted out
After you make sure your charging system is working right, and all your connections have been cleaned and recrimped, you might start looking at your battery.
I went through a battery every 3-6 months. I finally figured out that my problem wasn't the car, it was the battery. I had been buying them at Walmart. I finally had one of the clerks tell me that they fail all the time. I should have clued in on that when the last two times I went in, they didn't even bother to test the battery before offering me a new one.
I have since purchased an expensive spiral wound battery (Optima), and have been running without problems ever since (13 months and counting).