>Made by an AA airline machinist in Dallas, given to me by
>Mike Boland who worked with the fabricator.

>http://www.flickr.com/photos/syncronaut/6462855697/in/photostream/lightbox/

>Since I don't use the vent, that cap stays on as-is, held on with the wing
>nut.
>It's screwed on tightly so has never been kiped. ;-) As has already been
>described in this thread, the SS vent plate was removed, center-drilled
>and a small bolt put through it. No leaks.

>Bob

I haven't tried it, but here's a suggested place to start:

http://www.ebay.com/itm/ALUMINUM-5-1-8-CARBURETOR-COVER-HOLLEY-EDELBROCK-/120821028676

Perhaps too deep, but you could trim it off.  5 1/8" diameter seems perfect.

Regards,  Vern