I did a little mathing, and comparing the 1.625 and 1.700 intakes showed a 4.6% gain in surface area. The exhausts going from a 1.375 to a 1.44 was 4.7%. For my application, which is a mild street motor, I don't think it would be worth the cost. I'll just replace the springs and valve stem seals, do my own port work, and good enough.
At a reasonably safe 89% intake throat area, the gain is 10%, the curtain area would be up ~5%. But the gain is more than the sum of the basic math, the seat geometry & bowl form possible w/the larger valve won't be poss. with stock dia. units.
Jim K6