Just went through this on my buds 68 Coronet RT Convert

Performer RPM Intake - Intake fit fine , valley pan only

Then tried two of the four gaskets supplied in kit
Still fit fine

Then tried all four gaskets - No go , bolt holes wouldnt line up

So i used the two gaskets on the head sides only

Works great - Couldnt of worked out any better
Like i stated in my first post , let the intake dictate gaskets or not - Especially on aftermarket aluminum intakes