Roller Rockers 1.5 vs 1.6

You will most likely run into pushrod head clearance problem with the 1.6. I have ran those heads for years on a 340 with right around 500 lift and the push rod is right up against the head clearance hole as it is. my opinion going to a 1.6 would be a waste on your particular build if you want more go with more cam lift eventually unless you want to grind on those heads. 1.5 are a much better fit all around.