Right man. You loose only a few CR (10,8 for 3.0 and 10,1 for 3.2) wich isn't enough if you plan an high boosted engine. Wich is your goal? Wich will be car's useless? Track?Daily?
If you need an hi boosted engine you should use crank and steel rods from 3.2 with 3.0 block and use Z20LET pistons to lower CR enough to run on 1,0 bar over pressure. 3.0 use 86mm pistons wich are the same size of 2.0 and you might (not sure about this, check everything before to go on) have the same head desing from both ecotec generation engines (V6 and x/z engine series are all ecotec and IIRC 2.0 X20XEV/XER Z20LET/LEH... have same valves so I assume they have same valve angle and similar head spec).
This are my thoughts, I haven't any detail to be sure, I'm doing a simple brainstorming know how GM/Vaux/Opel had worked those years with engines engineering.
