The Silvolite pistons are cast and so are the least durable of what you can have. So putting in some hypereutectics or forged is a good step anyway, and you can get the CR up at the same time. Do you have the Silvolite S1267 pistons? If so, the zero deck makes sense.
Silvolite Piston - 5.6L Chrysler (V8) 1968-71 [1267] - $446.57 : United Engine & Machine Co. Incorporated, Performance Pistons
With those pistons, I too am getting around 8.9 SCR. Note that the stock 340 hi-comp pistons weren't really a lot more than that.... maybe up around 9.3 SCR.
1) Easy forged to get you to that old number of 9.3-ish is Speed Pro L2316F. Stock weight, so very little work needed for balancing if at all.
2) The KB243 hypers put you at the same SCR spot with less weight so a rebalance is needed.
3) Ross 99626 bumps you up close to 11 so that is too much.
4) JE's SRP line gets you to the same place as #2 and #1, and need a balance job. Ditto with Diamond.
5) Nothing else jumps out at me....
So, with the head as is, you are kinda limited to around 9.3. I'd be milling and new, better pistons. Or new pistons and different heads is really where I would go (and went).
As noted DCR is more important to look at and SCR is a component in that. Also the cam and its timing works into DCR and the application is a driver to the cam. So what are the uses for this car/engine? The cam selection kinda says what you intend, but it would be nice to hear from the source.
BTW.....That 3% number comes from the waaay oversimplified Wallace calculator. It only derives some misleading results that looks only at PEAK HP with one parameter in the thermodynamic equation. The effects of CR on torque at low and mid RPM's is much, much greater than indicated by that calculator, and it helps extend the usable RPM range. That improves mid-range HP more than is being understood; that is not being accounted for in anything that only considers peak HP. CR also contributes to items like cylinder clearing of spent gases and helps filling, and that is all overlooked in that online calculator. Working with less CR than you can pushes the engine operation further down in one corner of the map and limits the possible results. That particular calculator needs to go away.
