In my valley cover, there was a  "stud" that the screw would screw into.   this "stud a' was/is spot welded from the bottom side of the valley cover.  I removed the thing from the bottom side, then welded up the small holes where the spot welds were ( 3 of them ).  probably did not need to as they were very small, and there is a baffle there.  after this is removed a pcv valve and a rubber grommet can be installed directly into the valley cover with no problems. when I get back into town where my car is, I will try and take some pictures, if any one wants to see them.

Yes, I misused the term "stud". It is a threaded insert for the hold down screw that is pressed in and spot welded from the bottom. I want to avoid pulling the intake if possible.

I had to remove the valley pan. I could see no other way to remove the "stud" without damaging the valley cover.

In lieu of removing the hollow stud in that rear hole in the valley cover and especially for those cases where I might want to retain that hollow stud for restoration purposes, I have in the past machined a spacer that simply attaches to the cover with a ¼-20 screw or bolt where the original road draft tube attached.  Machining a lip at the bottom of the spacer allows it to remain firmly seated in place as well as allowing the oem gasket originally used for the road draft tube to be used.  A grommet and PCV valve are used in the newly installed spacer.  Here are some pics.
 

 

 
 

  
And here’s the link to the thread where this was originally posted.
http://forums.y-blocksforever.com/Topic142341-1.aspx

Lorena, Texas (South of Waco)

Now there's an idea. I have a lathe and I probably have some aluminum stock of the correct size. I may "borrow" that from you Ted. Thank you!

i removed the pcvvalve .instead piped the hose into the air cleaner so not going into the carb base. the fiting is past the air filter so does not plug the air filter'i use a after market air cleaner with a dry element. it al lhandels base pressure very well . just block the fitting into the holley carb