I have a stock 69 390 HP car. It has run perfectly for the 3 1/2 years I have owned it. I parked it in the drive, over night a couple of weeks ago to refinish the garage floor. Next morning, dead battery. I recharged it, etc. It definitely has dead short somewhere. Does anyone have any suggestions as to where I should start looking?

How old is the battery?  I've had batteries go bad with no notice indications with changes in seasons hot to cold or reversed.  Also for no apparent reason at all and they take a charge briefly  but don't hold.  I hope it's that simple.

I'm with Rick on this one.  My battery was going dead after I charged it so I figured I had a short somewhere too.  Until I disconnected the battery overnight and it still went dead.  Took it to Interstate batteries who tested it and said it had a shorted cell.  Whatever that means.  Anyway, bought a new battery, still disconnected it each night until one week I forgot.  Battery has held a charge ever since, without being disconnected.

Jim

What 'zactly do mean by "dead short"? If there is a dead short somewhere, all you would need to do is follow the smoke to the source of the problem. 
You say you charged it the battery....but then what? Would it not take a charge? Would it simply not crank fast enough to start the car? Did you charge it with the batt hooked up to the car, or were the cables off?

I would certainly disconnect the cables, and re-charge the battery first. If it sparks big-time when you re-connect the cables, THEN you know you have a short somewhere. No sparks, but slow/no crank, then you're looking at a battery problem.

The clocks in these cars are "on" all the time, so they do draw from the battery while sitting. This will drain the batt over a few days, if the batt is not up to snuff. Sometimes, the points in the clocks will hang, and have a big draw on the batt...sometimes a large enough draw to start a fire....not good!
A faulty voltage regulator and/or alternator can also cause a large drain on the battery.

My suggestion would be to take the battery out, charge it up nice, and then test it(or take it somewhere to have it tested), and then go from there.

after all of above. if you still have a drain the easiest way to trouble shoot the battery draining is to use a 12 volt test light. disconnect your neg battery terminal and hook the test light from disconnected terminal to the neg battery post. if the test light lights you have a drain. the brighter the light the heavier the drain a dim light would be a light drain. you can pull one fuse at a time to determine the circuit causing the drain. 

Thanks for the response...I will try your idea..It makes the most sense to me.. It;s definitely not the battery... It holds a charge indefinitly if I disconnect the positive terminal..

Donald, you never really said, but will the car start ok, but it just drains the battery overnight, or after a day or so?
If it starts ok with a hot battery, and then you disconnect the cable until the next time you start it, and it still starts, then you have a drain. I would start by pulling fuses one at a time,a s Bob suggested. Just remember, tho...with the door open, you will have a draw from the courtesy lights, so pull that fuse first. If you can remove all of the fuses, and still show a draw, I would go to the alternator next, and disconnect it. After that, go to the horn relay on the driver side fenderwell.
hth

For ElredJames, a shorted cell is just that, something has shorted out the cell...  not sure if you've ever seen the inside of a battery but, there are lead plates in there, alternating positive and negative plates. think of it like your left hand with your thumb up and your right hand with thumb up layed into each other, now add another 12 to 18 hands, connect the left thumbs(lets say negatives) and the right thumbs(positives) and you would have something very similar to a batter cell.  the plates do not touch each other with the exception of the "thumbs" for the positives, and the "thumbs" of the negatives. the acid/water mix is then added causing a chemical reaction, forcing electrons through the plates, and presto, you got electricity(dc anyhow)   now, if one of the plates make a 'connection' with the one next to it, it shorts out, effectively killing that entire cell(2.2 volts per cell).  this can happen by either a plate breaking maybe due to excessive vibration or a sudden shock, or maybe the plates 'shed' and build up debris that might make a contact between the two(not talking a long span, just a few millimeters between plates) or possible sulfation, which is usually formed from a discharged battery sitting for long periods of time.  the sulfur in the acid will 'settle out' of the fluid and build up between the plates, and once they build up enough, a short will develop...  hope that kinda helps.  been a long day,or days here for me(angel hasn't been doing to well, kidney stones/infection) soo...  I might have overlooked something.. :) 

Been there done that.  Have your battery "load" tested.  It can show a full charge but not pull a load.