Considering Compression Ratios

I continue to consider different ways of making the Mustang faster.  The challenge is that any performance improvement at this point involves replacing a relatively new part I installed with something better.  The gains are smaller without considering a larger engine.

If I went to a larger engine like a 347 or 363, I would need different heads that would work with a roller camshaft.  Bigger heads would have some form of improvement now so they would work for either option.  While I don't know that they offer a great deal of improvement in my current setup, I'm considering it and wanted to collect all the details I have on what different heads would do to my current compression ratio and if I switched to a larger engine later.

Looking through my original posts, I found the following detail on the original engine configuration.  If I plug it into an online calculator, the compression ratio is only 8.13 which does not seem right compared to the stock specs published online (9:1+):
    Cylinder Size: 4.040 x 2.87
    Deck Height: 7.365cc (.035" In Bore x 4.040 Bore))
    Gasket: 10.16cc (.047 x 4.10" Bore) (Fel-Pro 8548PT-2)
    Piston: 12cc Dish (Keith Black Silv-O-Lite 1157)

    CR 8.13 (w 55cc heads)

If I calculate where I am after the rebuild, the compression ratio is at 8.86 which is rather low.  I thought it was a little over 9:1 for some reason but don't see where my measurements are off.

    Cylinder Size: 4.040 x 2.87
    Deck Height: 0 (Zero Decked)
    Gasket: 10.16cc (.047 x 4.10" Bore) (Fel-Pro 9333PT1)
    Piston: 6.5cc (Keith Black KB115)

    CR 8.864 (w 60cc heads)    

The Summit website states that the compression ratio of the Dart 347 small block is 10:1 with a 58cc head.  The Summit site does not include a compression ratio spec for the Dart 363 but it does indicate the pistions are Mahl 93024485 with a 6.5 cc dish which would put the compression ratio at 10.7:1 with a 60cc head and 11:1 with a 58 cc head.  

The FelPro 10112 head gasket which compresses to .039.  The cc of the current FelPro 933PT1 is 10.169cc and the 10112 is 8.438 cc.  This has almost the same effect as dropping the head cc to 58.  This still only puts me at a 9.045:1 with the current setup.

If I use the FelPro 10112 and start to mill the head, I see the following impacts on the current setup:

58 cc = 9.266:1

56 cc = 9.5:1

According to a MotorTrend article I read, a change in 1 compression ratio is about a 3% change in power.  https://www.motortrend.com/news/0311em-power-squeeze/

My thought is that this really isn't worth the trouble.  I don't think the head would flow that much better and the compression ratio benefit is minimal.  The real difference is that I could have more than .550 lift and would be able to rev beyond 5500 rpm.