Rocker arm change

Ok so I am thinking about changing the rocker arms on my 360.

Set up as of now

1971 360
340 J head 2.02 and 1.60 valves
std bore flat tops
what we thonk to be the .509 cam

I would like to change the 1.5 rocker it had now to adj 1.6 rockers how much more clearance would I need.When I did this I would also rework the heads and have them ported.

What would 1.6 rockers bring my cam lift to and would it make it sound better.