365 GT 2+2 Fluid in the foot well

I have a 1969 365 GT 2+2. At the end of last driving season I noticed fluid in the passenger side foot well. I assumed it was the heater core and put the car away until this week. There wasn't a lot of fluid, but there was enough for the carpet to be wet. Unfortunately I did not taste the fluid when I cleaned it so I can’t rule out coolant. I began working on the car yesterday and ruled out the heater core because it is a) not inside the car and b) when I ran it for about thirty minutes I did not see one drop of fluid come out of either of the hoses into the car. So.... any thoughts as to what it could be? Could it have something to do with the evap lines. FWIW the A/C hasn't worked in twenty years but all of the lines are still there. Any help would be greatly appreciated.

 

Thank you for the responses.
1) I did notice a clogged drain tube last night so I cut open the end.
2) I thought about the battery because I did get a new battery last summer; however, I’m not sure how it could get into the car. I looked for holes and corrosion and didn’t see any.
Does anyone have any thoughts about this theory?
3) I haven't had the car out in the rain so I don't think it is residual water.

Edit: Just checked the battery again and it is leaking from the top. I will switch out the battery on Saturday and see if this is the cause. In the mean time, are there any other theories?

 

Thanks for the responses. The master cylinder is on the driver's side. The leak is on the passenger's side. So far the battery seems like the culprit but I am going to keep looking. As near as I can tell from the diagram in the manual, the only hoses in the dash on that side are the a/c lines and the vent ducts. There were TSB's in 1968 and 1970 about the vent on the fender and the one at the bottom of the foot well causing water in the car during heavy rain; however, the leaks have occurred on days when it wasn't raining.