2300 "D" port closed chamber Head

I would like to machine this head and get as much compression as I can. Where should I go to and still be on the safe side? 150, 170, 180, or higher?

Thanks
TC65

take it down just before it gets to the bolt holes. you can also angle mill it .depends on your casting. don't forget to use studs or shorten the head bolts. cant help you on shops . my shop is in mn

Unshroud around the intake valve too. Useless otherwise