Speedmaster, Edelbrock LA, or magnum cylinder head MILLING LIMITS & common Milling Optimization

When planning an engine build,

How much can SBM heads be milled?

(Closed chamber heads)

to reach 10, 11, 12 to one static compression for stock stroke 318 or 360 engines with:

Keith Black 167 +.020 (318/ 5.2 magnum piston Compression Height: 1.810 inch

Stats: https://www.summitracing.com/parts/...ENBFZ3ymXmnpBaYZqxu4a4s-V2Z520kMaAiNPEALw_wcB


OR

Keith Black 107 +.030 (360/5.9 piston
Compression Height (in.): 1.675 inch

Stats:

https://www.summitracing.com/parts/...q3G9sm0l7hWzRJe9zFBL144rWi9Tj3dnxeabERREPMaFE

I guess one would be assuming
stock (9.599” for LA)
OR
previous experienced deck milled heights, combined with

stock stroke, and available gaskets.

I am considering what compression I can run with the camshafts that I have on hand, the 90 octane nonethanol locally available, and 600 foot local elevation.

Google says:
The deck height of a Dodge 360 engine block is typically 9.599 inches for pre-Magnum A-series blocks, while Magnum versions measure slightly less at 9.585 inches

I am working with LA blocks, (I bet others would want to know magnum blocks as well)

How much can I safely mill the block deck height?

Which would you mill first or prefer? Block or Cylinderhead

If the combustion chamber is smaller, does that make the combustion significantly more efficient? (Which makes me lean towards head milling)

Or is this what racers split hairs with in order to achieve those last few horsepower numbers?- am wanting 180 or more cylinder psi if possible.
If 10 to one is 147 psi at sea level, I am wondering how to achieve this.

Thanks very much!!