Hughes Engines sells a kit that allows you to figure out exactly what's going on between the two surfaces, manifold and heads. It consists of a small thread of crushable "Wax Wire" that doesn't spring back once crushed.

The posts above on this thread contain a wealth of information on how to do an effective install once you've figured out the issue, or to skip the proper way and simply overcome the sealing issue with added sealant.

Either way once your intake is effectively sealed, it doesn't really matter how you got there as long as it stays sealed.

One step forward, two steps back seems to be a continuing theme with my Mopars. I just keep pushing forward, sometimes after a good pause.

http://www.hughesengines.com/Upload/TechArticles/INTAKE_MANIFOLD_SEALINGJULY2015.pdf

1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)