What year did Cadillac start installing radiator overflow tanks?

[C. Van Tune]

Did the '64s have them? 

[Jason Edge]

I believe it was introduced in 1969.

[C. Van Tune]

Thanks guys.  1969 is what I seem to remember as well. 

Guess I'm not going to be installing one on my '64, since it's a concours car.  It runs cool and doesn't need it, but an overflow tank is just something I like to have on cars. 

[Logan Robb]

I do not have a Concours car and think an overflow tank would be a great idea. Would this draw coolant back into the rad when it cools? Or would this be purely to catch it and keep it from hitting the ground?

Any good ideas about how to facilitate adding a reservoir/expansion tank?

[C. Van Tune]

Yes to both your questions.  

Super easy to mount.  I'd put it on the driver-side of the engine compartment.

Two mounting holes will need to be drilled.

Remove the factory overflow hose (it's at the radiator cap) and run a new, longer hose to the bottle. The "exit" side of the bottle will need a similar rubber hose going from the tank to the bottom of the car. 

I'd look for a nice condition vintage Cadillac bottle. Something from the '70s, so the patina and shape are more like what would've been used if it was standard in our era.  1969 was the first year that Cadillacs had them.