Well, while I was looking up blueprint info over at NHRA.com (
http://www.nhra.com/tech_specs/engine/ ), I looked at what they had listed for the L-78/L-89 option. They show 2 aluminum heads, casting #s 842 & 401, in 1968 & 1969, their valve sizes are 2.195/1.845, and they were available only on the Camaro. Now, I know this shouldn't be taken as "the gospel truth", but that is what the NHRA shows.