[trularin]

May I suggest:

The alternator will only deliver it's max rated current of say 65 amps ( standard 1960s alternator ).

The car, other than the fans, draws anywhere between 5 and 40 amps, depending on anything and everything "ON".

So, say the car draws 20 amps. The fans may have a max rating of 74 amps ( most probably inrush ), but for discussion purposes, let's just say 74 Amps.

20 plus 74 is 94 Amps. Subtract the best the alternator can do, 65 Amps, and you get 29 Amps.

This 29 Amps has to come from somewhere, hence the battery and a negative reading on the Amps meter.

If you can find one, a high current lab meter will give you a really indication of what your car draws.

You are probably beyond the changing system with the 74 Amp draw and the rest is coming from the battery.

On top of all of this, heat robs the changing system by as much as 20%.

Hope this helps.