Edelbrock Performer on 318

I am putting a 4 bbl on a 318 in a 68 Cuda. Replacing the original intake manifold with and Edelbrock Performer. problem is there is a short "stem" on either end of the top of the block, and a matching hole on either end of the original manifold. But the Edelbrock doesn't have the holes. Am I missing something here? Do I drill the holes in the Edelbrock? or do I file the stems down off the block? Anyone else ever encounter this? Nothing in the Edelbrock manual about this