How can you tell if it's a blown head gasket or the intake manifold?

I'm not sure witch iv got, I have heard that a bad intake gasket will do the same exact thing as a blown head gasket, that they will both mix coolant with oil, and I'm pretty sure I have coolant in my oil, on my dipstick it shows that I have a lot more oil than I should have and the last time I did a oil change I put the exact amount that I should put in, and also I can see like a green tint in the oil on the dipstick I rarely have started the truck up in the past two months but I'm looking to make it my daily driver. I already have my distributer off, intake manifold, TBI, and one side of my exausht manifolds. Before I go any further I wanted to know if anyone could tell if it is the intake manifold or a blown head gasket. My engine is a 350 small block, oh and my truck has been blowing a lot of white smoke out with water running out of the exuasht. Thanks and god bless.How can you tell if it's a blown head gasket or the intake manifold?more than likely on a 350 it's the head gasket, intake gaskets on the 350 seldom go bad.How can you tell if it's a blown head gasket or the intake manifold?Before you get too carried away did you have a cooling system pressure test done to see if you have internal or external coolant leaks? Small block Chevrolet engines aren't noted for head gasket problems unless the engine was badly overheated above 260 degrees.