I used a combination of plugs I made with tin snips for the larger holes, a spoon for the medium sized holes (both welded with a mig welder) and then leaded the small holes. The results are well worth the effort.
Before: http://picasaweb.google.com/ChrisAurit/BeforeAndAfter#5224669436113643378
After: http://picasaweb.google.com/ChrisAurit/BeforeAndAfter#5242108253679131842

[b]1957 Chevy Big Window 3100[.b]

In the Stovebolt Gallery
More pix in Picasa

It ain't broke 'til you can't fix it any more.