I'm putting together the crazy motor I got from the trunk of a
$300 145 and I had some questions:

I've got two heads (no snickers please).

One of them has been skimmed all to heck. I forget the actual
thickness but it is *thin*. It also has double valve springs,
hardened seats and good valve guides and such. It is casting
number 4 rag / hf30 / 460441.

The other is pretty thick. It has hardened valve seats but
it looks like someone ran a tap through some of the guides (knurled?).
This makes me less than comfortable with how long they will last
but I've often been told "chris -- you worry too much." This one
has casting marks 3UCG / BB27 / 470908. This head looks identical
to the other except it doesn't have a port for the air idle bypass
thingy.

I'm going to be putting this onto a block with .40 over pistons
and using a 2.0mm head gasket (instead of the more standard 1.2 or
0.8).

Is there any way to tell the compression ratio just from the
head thickness assuming the combustion chamber has not been
modified?

Does anyone have any suggestions as to which head is better?
thx,
chris