The 2.02/1.60 X heads should flow slightly better than 1.88/1.60 valve size. I believe there both 915 head castings. Combined with some headers you should notice a difference. 65'
To realise any benefit you may be looking at, run the numbers on David Vizard's 128 formula with the intake valve size you have now and the 2.02 heads. To optimize a change of LSA may be required. Higher ratio rockers would also help give more snap.
