Old Cylinder Head Condition after machining

[dom14]

Hey folks,

I dismantled and started machining the old cylinder head(one I pulled out couple of days ago) today. To my dismay I found a fair bit of pitting around the number 6 piston fire ring area, and a notable gash near the edge of the combustion chamber & more inside the combustion chamber wall(no idea how they came to be!!! but I'm guessing detonation?).

To my further disappointment I noticed the edge of combustion chamber and head surface is just about to disappear, indicating it's been machined too much(not by me).
So I measured the thickness and found out it is 105.5mm all around the head. The head was super flat and no warping at all. I just machined it to find out any imperfections and I found it as above. The below two links indicate the head thickness is 106.7mm & the maximum machining limit is 0.2mm(taking both the block and head into account).

http://engineproblem.com.au/headthickness.html

http://www.calaisturbo.com.au/showthread.php?t=41454

There is no block shaving ever(afaik). Obviously the head is shaved beyond it's tolerance as according to my measurement above(105.5mm thickness) and visually obvious smoothing the edge of combustion chamber & head surface.(see pictures). Obviously the head is shaved 1mm beyond it's limit.

In a nutshell,

Good

1. Head is flat
2. No cracks(there is a minor one inside one of the bolt holes that can be fixed without having to shave)

Bad

1. Head is shaved beyond it's 0.2mm limit(1mm to be exact, which is five times the limit)
2. There is still some pitting around the No 6 fire ring area that need some attention.

Is the head a goner for good?

Or can I keep it as backup in case of an emergency(combined with a thicker head gasket)?

Below are the high resolution photos hosted at google photos.

https://photos.app.goo.gl/mQDKtrGBKv5IM3ao2

https://photos.app.goo.gl/mnpSZCyaOzr5FIEB3

https://photos.app.goo.gl/2SaG0mMGW0szLvn02

https://photos.app.goo.gl/es9evUugPiWuDpct2

https://photos.app.goo.gl/Wf7MoINUkF4ydUbt1


P.S. I couldn't find RB30 head thickness anywhere in the Haynes manual. I had to google it to find out(as above links)