What would cause a edelbrock 350 intake not to bolt up in the center of a 350 block

Using a older 90 degree intake on a 72 degree bolt head. You can elongate the center holes.

Ok so I’m not a mechanic here is what I’ve found out the heads are not the original heads from the 87 block they have been changed believe the heads are correct heads so that intake which I have the center is not right due to that what in take would I need for those correct heads

Perimeter valve covers or center bolt ?
If they are perimeter the intake will bolt on unless it’s for 87 up heads.
Sounds like the intake is for the wrong year heads and needs to be modified to work or you need to get the right intake.

Elongate the center holes until the bolt holes line up