What is the common belief here on the use of RTV on the gasket between the lower manifold and the heads? I've purchased the stiff reinforced cardboard type gasket and wonder if I should use a sealant? And what about the gasket between the upper and lower manifold?

 

I always use the lower intake gaskets and never have a problem, I glue them to the block with contact cement and fill the gaps at the ends with RTV, never a leak. You definitely need a gasket between the upper and lower intake.

 

I put RTV around only the water ports in the intake manifold gaskets and the corners at each end as Paul mentioned. I install the upper to lower manifold gasket dry or maybe just a little high tack to hold it in place.