1978 ford pickup 150 302 engine?

This is condensation forming a foamy emulsion in your oil, when your PCV system is not operating properly either due to a stuck PCV valve or a plugged vacuum line you build up crankcase pressure until it blows this foam out any path it can find (if you look it will probably also be on the dipstick handle and tube) . Replace your PCV valve and if it continues to do this check for plugged/broken/disconnected vacuum lines on your PCV system.

Condensation is noted for these engines. Thy were noted for getting water in these engines. Thy did not have much EPA stuff on them, mostly a PCV valve was about the only smog thy had and thy would stop up all the time.

Changing the oil and putting in a new PCV valve. will fix this.

Did you do an oil change recently?

It is likely from water in the oil

I have seen this on older vehicles and in my mind water is getting into the oil somehow.

its condensation......happens more in the winter than summer usually.....can sometimes reduce it a lot or eliminate it by adding extra breather filters....like one on each bank + the pcv valve....