HELP-eletrical???

I grew up with and have driven ever since Station Wagons of the early to mid 70's. Currently I have a '75 to '78 LTD/Marquis that I am driving to deliver Pharmacuticals and I have a '76 Torino that is in storage because it threw a rod. My new bosses ordered me to get a pick-up, so I bought on e-bay a '74 Ranchero with the intention of fixing it with the Torino parts as they are (I imagine) the same to drive since they are virtually identical with the exception of the roof behind the driver's seat. I got it started, them the next time I went to start it the battery was dead and tested bad (OK, It was the battery out of the Torino and 5 yrs old). I replaced the battery and it started, but the next time I went to start it, the battery is dead and tested bad. I replaced the battery again, same results.Yesterday I exchanged the battery under warrantee again and again it started. I started it, checked the alternator (14 Volts), drove it around the block, shut it off. I did this 4 times, each time the the volt meter said the alternator was putting out .1 or .15 volts less then the time before (still acceptable as it was still above 13.5 volts. Today I go to start it and the battery is totally dead. HELP, what gives???

It sounds like you have a fairly heavy drain on the battery even after the ignition is switched off...
A short in a non-fused and unswitched circuit would drain the battery like you describe.
If you have access to a ammeter, disconnect the positive battery cable, and put the ammeter in circuit from the battery to the cable. If it shows a draw with everything switched off, it's time to get out the wiring diagrams and start isolating each circuit 'till you find the one that's shorted.

A good source for info specific to your new Ranchero is the Ranchero.us board at http://www.beef-cake.net/cgi-bin/Ultimate.cgi?action=intro
Generally you'll get a faster response there too.

D.B. is correct that you have an overnight drain that is zapping the battery. If you are having the problem I think you are ( not just draining but destroying the battery) I would suspect the short in
the voltage regulator. When heated ( operating ) the circut will close supplying the voltage needed to operate and recharge. At rest it "may" be shorting to ground and burning cells in the battery . It took me a while to find this problem on a Rustang once . I have allways opted to upgrade to a one wire internal regulated alternator on all my project vehicles. Saves time and effort in troubleshooting.