Blown Head gasket or intake manifold?

[fostrem]

First off my truck is a 76 k10 with a 350sbc in it. The reason I got to the conclusion that it was a head gasket was that it was smoking a ton. It would billow out the exhaust and the once the truck heated up, some smoke would come out of the left side of the engine. The truck barely runs as is. It can barely idle and eventually dies if i don't mess with the throttle even though the idle is set high. I set the initial timing to about 10 degrees but haven't been able to set total because the thing won't run long enough. I think its the head gasket. I checked the coolant over flow tank which was bone dry and when i drained the coolant, it still had a nice green look to it, not milky and no traces of oil. I then checked my oil which had a tinge of gas smell. Before I rip the heads off, do you think it is the head gaskets? intake manifold gasket? The only thing that worries me is the amount of smoke. The smoke is white ish and is not steam it smells like burning gas/oil.

Thanks in advance