The main advantage of 1.7 rocker arms over 1.5 or 1.6 rocker arms is faster valve acceleration rate off the seats for more cylinder filling for increased low end torque. The valve duration would be increased slightly by four or five degrees.
The increased flow and HP produced with 1.7 rockers at high RPM HP is negligible. The low end torque increase may not be worth the effort it takes to fit the 1.7 rocker arms, i.e: valve spring open height, valve train geometry, pushrod clearance and pushrod strength. Higher ratio rocker arms moves the pushrod about .060" closer to the rocker arm pivot point and places more lateral load on the rocker stud and pushrod. The rocker studs should be ARP 7/16"-20 when used with 1.6 or 1.7 rocker arms and the pushrods should be .080" wall, 5/16" chromemoly.