If you take .100" off a head on a 170 that's already at 8:1 (it's almost certainly around here or lower) then you get 10.5:1. You are also getting the valves pretty close to the piston.
The 170 has different lobe separation requirements than a 225. A 225 with stock size valves needs about 105° LSA for optimum torque across the power band, the 170, 112°. If you go with oversize valves the LSA decreases about 2° in both cases. In my opinion, most performance build 225s have too wide a lobe separation and too much duration, but many are crutched with advanced cam timing. This works okay as the intake valve closing point has a larger effect on how the engine runs than any other valve event such as exhaust opening/closing.
Read this:
http://www.hotrod.com/how-to/engine/060 ... ft-basics/
If you want a seriously considered cam recommendation you need to tell us what fuel you want to use, the true compression ratio and how much time you're willing to invest in tuning. The condition of the short block is important too as worn cylinders and rings will pass oil and induce ping.