install pdf 6019-dp?

The 6019-DP manifold is designed to be heated by the exhaust manifold (same as the original Ford design).  The intake should be attached to the exhaust manifold at the “hole” you are referring to in your question.  A water plate can be used to provide heat...

Horse power, torque, mpg

Will you be using a Dual Port or a “C” Series intake manifold.  Also, will you be doing any other changes to the engine?

Chevy 6 intake manifold

White Owl Speed Equipment has that manifold in stock.  You can contact them at 559-786-1864.

Offenhauser 6115

Thanks for the question.  There has been talk about doing a production run of the 2.6L dual port.  Although the 6115-DP is a limited manifold for the U.S. market, we understand that it is more common outside the U.S. and that is why we are considering a production...