"...Do you think chamber work alone will see me right?..."


Any amount you add to the chamber size will reduce the static comp. As said, the ACTUAL final cc size is the number that counts. And there is no way to know that size other than to actually measure the chambers.

And that "factory specs with stock parts" deal, could mean lots of different things. One site I found says that most Pontiac engines came with .023 deck height. So, did they leave it at .023 ? Or did they cut some off the block deck ? Did they resize the stock cast rods. These things affect the static comp.

Also, you mentioned 4-relief pistons. The 8-eyebrow pistons will reduce comp. The L2262F Speed-Pro pistons will increase comp, over original stock pistons and the 8-eyebrow kind.

So, depending on EXACTLY what all the specs are, you may not need to enlarge the chambers any. Since the heads are off, you can measure the deck height, and get the part number off the top of the pistons.