If I recall correctly, enlarging the valves to at least 1.86"/1.6" intake/exhaust was one of the biggest gains. The bolt-in lumps gave a 5 - 7 hp gain throughout the entire rpm range. The lumps didn't provide any benefit till the valves were enlarged.
One thing that "just bugs me" about the 250 large combustion chamber, is the overlap of the combustion chamber with the deck surface of the cylinder block. This cannot be conducive to flow. And, I am not partial to grinding and tapering the top edge of the cylinder wall. The 194 combustion chamber should be able to avoid this. To help reduce this overlap with the large combustion chamber, offset cylinder head dowel pins have been used by some. However, I have not found a source for cylinder head dowel pins with offsets of greater than 0.030". In the Power Manual, one engine builder gave offsets of 0.060" to 0.090".
