depends how much has been milled off it and what the comp ratio it is.
to work it out u basically need to find out how far your tdc piston to deck height is, what type of piston u have whether they are dished or flat, then u have to have your combustion chambers CC'd.
Calculate all that and youll have your comp ratio.
If your pistons are stock you can look up the cc specs via the net or a gregorys w/shop manual, a head specialist can cc the chambers for you
I think anything below 10.0:1 will be ok for turbo.
you can also use a cometic head gasket which will lower the CR and are far superior to standard gaskets ie felpro, acl ect ect but this deems a milled head pointless of being fitted and your original would be best anyhow
has the offered head been ported??