I'm running a really nice set from Pro-Mac Carbs. I looked at all the offerings at the 2005 Nats and the Pro-Max ones popped out with the thick flange, steel inserts at all the hold down points and flawless TIG beads. See my newbie intro (rumblefish72) or go to Pro-Max at
http://promaxcarbs.bizland.com/Engines.chtml Scroll to the middle engine to see the covers. I had to grind just a little bit on the inside of one of them to take some inside TIG bead off. It interfered with my Mopar Performance aluminum hold down blocks. The end blocks are pretty chunky. I trimmed the blocks by 0.050" on the Bridgeport (outside only) and everything fits nice now. These covers don't have any hole in them. I'm toying with the idea of putting a GZ Motorsports (
http://www.gzmotorsports.com/) street vacuum pump on my car so no holes is a good thing. BTW, several manufactures (K&N) sell bolt on breather kits. You drill a 3/4" hole and bolt their breather mount on (no welding).
I'm running Edelbrock Performer heads, a 0.550 lift Comp mechanical cam with Crane Gold 1.5 rockers. Edelbrock heads have a raised valve cover rail so interference isn't a problem.
The billet covers look very NHRA pro-stock .... I'd buy these covers again if I was in the market.
-Rumblefish72