Some how I lost two nipples and hoses that vent the valve covers to the flame arrestor. These are the same size as stock valve covers. The hose is 5/8 and I believe the plastic nipple is 3/4.
Any ideas?

Most use something like this. http://www.summitracing.com/parts/snn-10075/overview/

Ordered two, and did not fit. I am not taking valve covers off to enlarge hole. Engines are already installed. There has too be hundreds just laying around on engines that have been pulled.

You can search under hole size at summit and they have a million different ones.

http://www.keitheickert.com/c-352-breathers.aspx

PM me if you have any questions.

The push in breathers should have worked. They all use the same size VC hole. Sometimes the rubber grommet that is inserted into the VC can really be tight and seem impossible to push the breather into, but they should all be the same. If you have an old grommet lying around use that instead of the new one. May be easier.

Perhaps you are trying to use the hole that a pvc valve would normally go into. In which case yes you are correct a breather would not fit. Any auto parts store should have the plastic piece your looking for. Probably hanging up on a revolving rack that has little door clips, grommets,etc.

This is what I am looking for.

[ATTACH=CONFIG]523415[/ATTACH]

I would check at the main NAPA store on Grover St.

That looks like same diameter as a PCV valve, any auto parts store should have them.