The M30 head will be warped when you remove it - either due to the original
problem, or just the act of removing it.  The front of the timing chain
cover
needs to be planed (re-surfaced) at the same time and depth as the head.
Might as well replace the timing chain.  Check the camshaft lobes for wear
and replace the cam if needed.  A mild porting job will give you 10hp or so:
while you have the head off it's cheap.  You might also consider a set of
headers, which could give you another 10-15 hp.

Be real careful re-torquing, with new bolts.

FloydR