Newbie question, Don't laugh too hard.

[688ANAV]

Hello Everyone,
Thanks in advance for everyone’s input on this extremely informative site.
Sorry to ask such a basic question, but I have to.
OK, Newbie story..
My Father-in-law (awesome restorer) is currently finishing the body on our 69 Camaro, Yenko Tribute Car. Sorry it is only a tribute car and not the real thing. I have been doing the research on correctness for the last 4 - 6 months or so.
Very 1st basic question that Internet articles and many of the websites do not agree on is this...
The Heads.
Aluminum or Cast Iron?
We have access to a nice period correct block but I've been pulling hair to find a period correct set of aluminum heads because that’s what I have read on a few websites were used. I do have internet skills and have scoured many of the Camaro research sites, but there is little published data for the heads. Only that the ZL-1’s were all aluminum block, head and intake and L-72 427 Yenko motors were steel blocks with some reporting aluminum heads. I have yet to find a casting number in Aluminum if that is what was truly used. I have found casting #’s for the 1969 L72 cast iron heads though (3919840). Any input would be greatly appreciated, we are not attempting create a scammers car but would like as many of the items as possible to be year and casting #'s correct.
Thanks again in advance and sorry if this was posted in the wrong area.
Tracy