ZL-1 & L-88 head design clarification

[nuch_ss396]

Hello,

I am doing some research into building an L-88 engine for
a project. I know the L-88 in 1967 used a different head,
but I'm not sure what it was. I'm trying to determine
which heads were used in the 3 year L-88 program, which
heads were used in the ZL-1 program, and how the cross-over
between the L-88 & ZL-1 programs worked ( if at all ).

I've been told the L-88 ( 68 through mid-1969 ) may have
used the '842 closed chambered heads. Sometime in mid-
1969, the ZL-1 came into being as did the '074 open
chambered heads. Is this where the cross-over happened?

Here are some questions:

1) Were all L-88's equipped with aluminum heads?
2) The ZL-1 was open chambered, but when did the L-88 go
that same direction? Was it also mid-1969?
3) Where does the whole LS-6 program fit into all of this?
4) Does anyone have an example of a closed chambered L-88
piston, open chambered L-88 piston, ZL-1 piston that they
can post pictures of?

I thought this would have been easy to figure-out.

Steve