Fired my '59 F100 up today for the first time since I bought it. All the suspension/steering work is done, along with carb rebuild, plugs, points, etc.

Fired right up. Ran good, idled nice and smooth. I let it warm up to get the oil warm for an oil change .... Antifreeze came out with the oil! Noooooooo

Am I correct that a blown head gasket would be the culprit? Any other easier options I should check first?

Help a F100 newb!!

 

You could try and retorque the heads. My guess would be the head gaskets.
Was the engine rebuilt or is it original?
If it was rebuilt the heads may not have been trued up correctly or the gaskets may not be installed correctly.

 

It's original and never been rebuilt as far as I can tell.

 

Head gaskets would be the most likely (and least expen$ive) cause. Intake manifold is another possibility, as I believe Y-blocks had a coolant crossover (you don't say whether it's a 6 or V8, tho...).