slant 6 exhaust manifold

No, you need to get a good intake/exhaust manifold gasket, after you've bolted the two manifolds together (off the car) and made sure that they're true.

http://www.fcrcmach.com/new-remflex-exhaust-gaskets-mopar-slant-6-22562256196083.html

In my opinion, the manifolds are too much of a pain to get on and off to have to go back and solve vacuum and exhaust leaks.

http://slantsix.org/articles/Slant_...n/Slant_Six_Exhaust_Manifold_Installation.htm