1970 Chevrolet C20 Pickup - Motor Leaking Oil

[ggalv]

Here are additional pictures. I have had the truck for awhile, but don't drive it too often and I assuming that missing hose/cap has been there all this time (see "Revision" below). The truck has ran well, but right now it's not running too good. I have been driving it around a few blocks every week for about 2 months. When I press on the gas pedal, at 10-20 mph I noticed the truck does not respond well, feels like it needs more gas, not getting the power. I am assuming this opening in the valve cover gasket does not have to do with this, since that opening has been there all this time? "Revision" - actually I had a new carburetor installed about 2 years ago, not sure if the hose that is supposed to go their might have not been installed, but I don't know, maybe it has been without the hose/cap since I got the truck. A two barrel carburetor was replaced with a four barrel carburetor. Might provide a separate thread with more detail about the truck not seeming to be getting enough gas/power and the work that has been done.

Based on the additional pictures, might this help to figure out if what is currently there correct and what I need to put in that valve cover opening?

Appreciate your help.