There ya go... that's how it's done. With those numbers above, I get 8.6 SCR with a 1.755 CH (.067" below deck) and no eyebrows but adding 1 cc for the gap down to the rings, a .028" thick head gasket. So that is close to your 8.78 number.
For milling the smaller area of the 302 clamber mean you will have to mill something like .007" for each cc taken off. So milling .020" would get about 3 cc's off and if the chamber start at 65 cc's then that 62 cc result would get you to about 8.9 for SCR. Getting better. I'd go at least .030" and also measure those head chamber volumes carefully, they may be smaller than you think. If you get the chamber down to an actual 60 cc's then you get to 9.1 per my numbers, again, using the .028" thick head gasket.
With that, you are at around 7.3 for DCR IF you advance the cam timing to an ICL of 104. That is a ton better than where things were heading before.