You've undoubtedly got a narrow deck crankcase, and the engine gurus I've talked to got agitated when the topic of conversation got around to higher compression ratio because the crankcase could be more prone to cracking.
My suggestion is to live with the lower compression ratio and lower power. Do the math and figure out how much more cruise speed you'll get from a higher compression ratio (when I did that exercise on my RV-8, I think it was only a few knots) and how much more rate of climb you'll get.
If you've got an O-320 in a -3, you've got a rocket ship already. As for a constant speed prop, your plane is probably at a forward c.g. already, and the constant speed prop will likely take a little bit off the handling.
RV-9A at KSAV (Savannah, GA; dual G3X Touch with autopilot, GTN650, GTX330ES, GDL52 ADSB-In)
Previously RV-4, RV-8, RV-8A, AirCam, Cessna 175
ATP CFII PhD, so I have no excuses when I screw up
Vaccines kept me out of the hospital but COVID still cost me a month of living, all told...