GM 3100 bad head gasket???

[69heavychevy]

Hey guys,
I wanted to get some input on a car I'm working on 2001 Chevy Lumina 3.1. The car was puffing out steady white smoke so right away I figured bad head gasket. I check the oil and its clean, no signs of water contamination. I check the coolant in the reservoir and it looks like mud. I crank the car up with the radiator cap off and right of the bat its shooting coolant out through the filler neck. I go ahead and do a block test and the tester fluid turns a light yellow. Everything points to it being a bad head gasket but why is there no coolant mixing with the oil? Also will a bad lower intake manifold gasket cause all the symptoms of a bad head gasket?