This engine is a single in block cam engine so there should be no high pressure oil going to the heads across the head gasket. If the head gasket was blown you would get the classic water in oil and not oil in water.
The radiator on these are a single unit containing the engine cooler and a transmission cooler, if you have an automatic transmission. Both the engine oil and trans oil passing through the radiator should be higher pressure than the water which is good news for you, there shouldn't be water in places it can damage, oil in water doesn't do much. This is also the only point where they are close to mix if there was a break and has potentially higher oil pressures than the coolant pressure.
thoroughly check for any cracks or damage around the fittings on the radiator. If you want to go crazy you can hook up some test line to the oil inlet, plug the outlet, hook up some compressed air, and see if you hear hissing inside the radiator.
I am pretty confident it is your radiator though.
If it is not your radiator the only other place that higher pressure oil and water could mix is by a very strange crack in the block that only goes between a high pressure oil spot and somewhere that there is coolant. I give this a almost completely unlikely chance but stranger things have happened.
A side note: you may also want to check your trans fluid if it's an automatic. see if it's low or milky.