Don't know if you are aware of this, but those blue fel-pro gaskets sometimes don't seal very well with aluminum intakes. I would use a Fel-pro 1256. I don't think these have a steel core so they should be easy to trim.
http://www.jegs.com/i/Fel-Pro/375/1256/10002/-1
Here is a link with a scan that shows where Edelbrock says DO NOT use the blue permatorque gaskets.
http://67-72chevytrucks.com/vboard/s...d.php?t=528147