Your power goal is very doable without sleeving your block. Bore out 0.5mm so that you have a true bore, and hone. 9.0:1 is kinda low for my taste. I would do somewhere 9.6-10.5. I used 9.8:1 81.5mm CP pistons and eagle rods for my set up. Get your crank micropolished and balanced, and use new bearings. You might max out your 550cc, so look into 750cc. Prepare to spend big money for everything. Good luck!