This is after the fact, but, those 170s may be a little small for your 347. That being stated, I'm running 170s on my 333 (.040 over; 5 bolt 289). I'm running TRI-Ys with a Performer RPM. These are great heads and make great power if teamed with the right cam and valve train. I'm assuming your looking for a good street warrior?
My TRI-Ys work great with plenty of road clearance.
Good Luck!