1970 Chevrolet C20 Pickup - Motor Leaking Oil

[ggalv]

Hi, regarding the how many miles question the odometer has 40426, then it has an 8 with a white background. Not sure how many miles would this be?

Below is a picture I took today, not sure if this might be where it is leaking oil. I had the starter replaced recently, and it was covered with oil. Should some hose or some kind of cap go in the valve cover opening (circled in red)? Also, there seems to be a decent amount of oil in bolt (circled in red).

Appreciate your advice, on where this oil might be leaking from?