What's a Power Pack head look like?

A buddy recently picked up a 1961 283 and some heads. We were told they were power pack heads, and they have a funny little rectangle pad where the 'double hump' would be on a set of other SBC heads... Is there anything that sets power pack heads apart from regular heads, or any visual clues to help ID these? What is the difference?

Thanks in advance for any help!

 

I believe those are 2-bbl heads. The power pack 4 bbl heads had a little piramid on top of the rectangle. The 270 HP 2-4 heads have two towers on the rectangle.

 

yep, you got the 2 bbl heads

 

Gracias! That's good stuff to know, thanks!

 

You will get a more positive answer if you post the casting number in the head.