Again bought this truck. Only fill cap and pipe were connected to nothing. Just hanging in hood. Which side, if I'm looking at the engine from the front bumper, does the oil go?

 

look on the top driverside valve cover, should be an open hole and rubber grommet near the front that the filler tube slides in

 

there is a hole but its on the passenger side. My concern is someone may have, at some point, put the valve covers back on backward.

 

The fill hole and the PCV hole both are supposed to be in the driver's side valve cover. There is a hole in the passenger valve cover for the breather assembly that in turn has a hose running to the side of the air filter. It's also possible someone changed the driver's valve cover and did not put the correct one on.

 

It looks like the covers are reversed. Does that do damage to the truck?
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How about you take a picture and post it to show us what you see???

For my 99 3500 van, On the driver side front of the valve cover is the hole for the oil filler tube as described earlier, it seats right into the valve cover if it is the correct one. At the rear of the same side of the valve cover is the crank case breather element that is attached with a hose to the air filter cover.
The passenger side has only the pcv valve connected to the rear top of the valve cover and the hose runs from there over to the driver side of the manifold

doubt if there is much damage but probably would run lots better hooked up as it is designed to be

 

That all different from mine, perhaps the V8 and V6 have different setups.