I removed the stock cast iron manifold gaskets from my 327 Gen-I, cleaned them up and installed new gaskets. There was some build-up on the heads and manifolds which I scraped off as good and straight as possible, include wire wheel. I've attached a picture before I completed all the cleanup.

Anyway now they're back on with new Fel-Pro gaskets (steel composite, multi-piece). Doing a blow back test with soap, the center ports are leaking severely on both sides of the engine.  I've double checked bolts and they are torqued down.  Should I take the gaskets off and add some Copper RTV to both sides of gaskets and reattach?

The manifolds looked pretty straight to me and not warped, but I did not check with a straight edge.  

Thanks for any advice.

You could try reinstalling the gaskets using a thin layer of RTV silicone sealant.  But it is possible your intake manifolds are slightly warped, since it is only the center that is the problem. You may need to have them machined to ensure perfectly flat mating surfaces. (This is a common practice with older engines.)

I could almost guaranTEE the manifolds have some warpage. Not sure about the particular gaskets you used, but I would suggest either the factory style, lead type gaskets, OR, the best gaskets I've ever used on cast manifolds, header gaskets. The old style, thick header gaskets work best when soaked in water for a few minutes, then installed while wet. Cut the gaskets into 3 pieces to make it easier. Get them tight, start it up and let it run until the gaskets have completely dried, and let it set for a few hours/overnight. Then crank down on the manifold bolts one more time. 9 times out of 10, these gaskets will permanently seal cast manifolds. If they do not, then it's time to get the manifolds surfaced. 

Thanks for those suggestions.  I'll try those ideas.

Here is a photo of the gaskets I bought and currently have installed.  They are "steel, composite".

I have used the three piece ones, as well as "Mr Gasket" ones. They both worked with no problem.