[Michael C Henry]

If you are not mechanically inclined you to find a friend that is. The Flaming River battery disconnect switch is a great idea. That is one of the fixes I used. The original builder used the smallest battery he could get away with. He had a master switch on the fire wall incorporated with the Ford starter solenoid, a neat looking arrangement. the switch lever- knob is accessible from inside up under the dash, not reachable when the seat belts were on. I'd be expecting to only be a quick moment and not turn off the master switch. the heated coolant would rise and collect in the top of the engine and radiator , turn on the electric fans and the battery was dead. I went to a larger (OPTIMA) yellow top battery and installed another master switch, in series, (Flaming River ) on the dash in plane sight and accessible from almost any where. Twist the red knob on and bump the knob inward to turn off. The Flaming River master switch has a bypass circuit to keep things like my Mallory HyFire V1 CD box memory. But that is not the main fix you still need to find where the current is bleeding off to.
Testing the battery, disconnect the battery from the car, fully charge it and then let it sit disconnected for a day , reconnect the battery to the car, if the battery is still charged it is not the battery if it isn't still fully charged I'd suspect a bad cell in the battery. Really active batteries discharging an recharging can cause the metal plates in the battery cells to flake and have the metal flakes fall to the bottom of the cell, accumulating shorting out the plates in the battery cell in the battery. Current may be something leaking small amounts of current over a long time or something is on or taking way too much current. If that is happening then you still need to find the current bleed off. It could be a combination of things now all happening together.