[Mr70]

"The pre-1970 open element bases were lower ( due to increased
intake height ) and the 1970+ were higher ( due to reduced
intake height ). Does that about cover it?"
....Bingo!

No..the ZL/2 Cowl Ind. hood & AC was not the same as the flat hood used with the OE AC.I've heard reference to the second design Z/28 hoods,but I'm not really that familiar with them...rib structure maybe?
This is 1st gen Camaro mecca,so someone else here should know for certain.