[vectorit]

To me it looks like someone has tried to fix the valve cover with a home made spreader. I would take the valve covers off, make sure they are not warped, then use a new cork valve cover gasket with a good sealant.

The fuel pump area looks to be a possible contributor to the problem.
There is a bolt hole in front of the block that if not plugged with a short bolt, it will produce an oil mess but not as bad as yours.

The fuel pump gasket could also be bad, and can cause a big mess of oil spray due to the fan blowing it back.

Below are pictures of what I am talking about.
In my case in my '70 k10 it had a huge mess of oil all over the passenger side, and I found the culprit to be the fuel pump gasket. Apparently it had been this way for a long time.

In your case I would take the truck to a place where you can wash the engine down with a high pressure hose, then look for the leak when you get home. Your engine has a lot of fresh oil all about, so the leak shouldn't be to hard to spot after you get all the mess cleaned up as best you can.