<<Could you explain this. All it takes is a different fly cutter to put in seats. The guides were the same size. The castings were basically the same in configuration.>>
Photo below is a 461 chamber with 2.02/1.6 valves, but it's similar to the 462/291/186 chamber; note the added machining cut to unshroud the side of the chamber wall adjacent to the intake valve to optimize flow. Tonawanda only built small-block heads with 1.94/1.5 valves and no unshrouding cut, and didn't build any solid-lifter small-blocks; all solid-lifter small-blocks (and hydraulic-lifter L-79's) used 2.02/1.6-valves, and they were built only at Flint V-8. Flint had the transfer line station for the larger valves and the unshrouding cut, and Tonawanda didn't.