I'm betting its the LIM gaskets again. If a head gasket was blown to the point of allowing that much coolant into the oil, you would have combustion gasses making their way into the cooling system.
Do your radiator hoses get a lot of pressure immediatly after a cold startup?
Did you pull the plugs to check for discoloration and moisture?
When your LIM's were replaced, were the fel-pro metal framed ones installed or the standard GM plastic ones?
You can remove the UIM, LIM, and once the LIM is off, check to see if you can find a leak.
I just got done putting a second set of LIM gaskets into my g/f's 3100 GP SE. Now we are trying to find a part number for a 180 stat so I can tune her fans to come on at different points with my powertuner in hopes of not blowing a 3rd set of LIM gaskets.....