Vortec intakes only have 8 bolt holes. The vortecs don't have center bolt holes. The older intakes are 12 bolt. All enter bolt heads aren't vortec heads although many may call them that. Of the older 12 bolt intakes there are two different ones. The older ones are all angled the same. The newer ones have the four center bolt hole angled different from the rest.
There are a one or two years that had 4 bbl carb aluminum intakes. Those engine had center bolt heads. The heads with the four center intake bolts that are angled different. I have one of those intakes. I believe it was in a 87 grand prix.
Edelbrock 2104 or Summit SUM-226016 will work on early center bolt tbi cylinder heads but not the vortec cylinder heads.
You can modify the older 12 bolt intakes to allow them to work on early center bolt heads.
http://67-72chevytrucks.com/vboard/s...d.php?t=180289
Best bet would be to get the cylinder head casting numbers. Find out what cylinder heads you have and get an intake for those heads.