Hmm. This sounds like the same question on the Yahoo Group, but the photos are interesting. I'm about as far from being a mechanic as possible, but I'd ask:
1. How does it run? Still strong? If it does, it shouldn't be a blown head gasket.
2. How do the plugs look? Tan, or oily?
3. What's the condition of the airbox? Any oiliness in there?
Reason I'm curious, if one of the oil breather lines was blocked and you were getting oil blown into the airbox, it could be pushing an oily air mixture through the carbs . . .
Though I wouldn't expect a leak unless the intake tubes were old and porous . . .