I know this has been covered, I couldn't find the search engine. Regardless I am replacing  the valley cover with the rear breather tube style.  I understand to get a tighter fit to drill holes for sheet metal screws.
I am thinking one near each corner and two space on each side.  I think tapping for small bolts would be better than sheet metal screws.  The valley cover is a tight fit between the heads at the intake flange. Should I just pop it in or grind a little radius on that sharp flange edge
Regarding PVC Valves:  I understand I can use Nappa help # 42324 gromet  Napa # 2-9200 PVC
I have a Holly 600 cfm double pumper manual choke. Do I run the PVC hose to  a vacuum port.  Is this all I need to do aside from blocking off the canister breather. Do you have to remove the threaded boss for the breather tube? 

The valve cover breathers are not functional