i know people that have milled .080

TO answer your question its not worth the increase in power. You are better off buying a GSR head (automatic .3 bump in Comp from the square chamber) and running flat faced valves (.3 bump).

RUN AN OEM HEADGASKET ALWAYS.

That would be a .6 bump in compression from just switching heads and valves. Much more reliable that milling past the service limit.

Milling the head screws up your timing too because you are shortening the deck height.

most i would do is .010

from that you might pick up 5whp. maybe a little more if tuned.

Or you could buy a header *COUGH IN STOCK COUGH* an make 10whp