First time I used ACDelco RTV- My favorite hands down, never had any problems ACDelco 88864346
Second time I used black rtv stuff from the autoparts store. I'd have to go dig it up to see what brand.
Both times around coolant ports (only on one side, the other has a ring thing in the gasket), the second time I was extra careful in making sure sealing the valley wall didn't interfere with the coolant port in any way.
