Hope everyone is doing great,cold here in Missouri and snowy, this might be a dumb question but I am having a hard time getting an answer.I bought some reproduction original chrome valve covers,the breather hole on right side cover has a 1" hole and the driver side has a twist on hole for a twist on oil cap.I have an aftermarket air cleaner and I need to know what breather and oil cap I need to use.My car always had aftermarket valve covers with the 1.25 holes on both covers but i did not like the finish (the chrome finish on the new covers really look awesome) any help would be appreciated. Thanks,Allen

If it's an open style air cleaner, you'll need a push in type breather (Mr. gasket brand works) the oil fill cap should be a stock type.

Oil cap:
http://www.rockauto.com/catalog/moreinfo.php?pk=48455&cc=1249264

Breather"
http://www.summitracing.com/parts/mrg-2068?seid=srese1&gclid=CN7F6LvGv7wCFUJrfgodhCUA8w

Thanks doc, but the pass. side valve cover is a 1" hole ,center of rubber grommet 3/4" but the oil cap might work.I was hoping someone might be able to give me a stock number for the original chrome oil cap.I could then use it as a reference number to crossover Aftermarket breather is my only chance for pass. side cover.

If I were you I would plumb my air cleaner to accept a breather tube and use a PCV in the valve cover on the pass side. Then just use a regular oil cap on the drvr side. The PCV is basically a one way valve and just replaces the open tube that was original to the motor.

The hole is one inch to fit the grommet the push in breather will either have a one inch grommet with it or will be 3/4" to fit in the grommet in the cover.
The breather in the valve cover will let air into the engine and it is removed through the PVC in the vally cover giving you crankcase ventilation.