On the mid-year 1955 to 1962 235 and 261 engines, the water pump was moved lower on the front of the engine block, and the pump impeller protrudes through about a 3" diameter hole into the front of the block. Earlier engines, 216 and early production 235s have the same water pump, one that bolts onto the front of the block close to the cylinder head and pumps coolant through two holes in the block. The position change was necessary for fan clearance when the midyear 1955 trucks went to a lower hood profile. If a late style engine is installed in an earlier truck, the fan to radiator misalignment causes cooling issues because a very small diameter fan must be used, and it doesn't pull sufficient air volume through the taller radiator. An adapter plate is sold by a stovebolt.com member (Pre-68 Dave) to make the early style pump fit the later block. It works very well.
Advancing cam timing increases low end torque while slightly reducing high RPM horsepower. Since the stovebolt six has a long stroke and it was engineered to produce lots of torque already, I don't see much advantage in advancing the cam timing, unless you have an engine dyno and enough experience to evaluate the results of your modification. On the small block Chevy V8s I built for round track racing, I found that about 3 degrees of cam timing advance worked well, especially since the class I was building for was restricted to a low volume carburetor and high RPM was virtually impossible to achieve. Doing race engine stuff on a street engine is stupid squared, in most situations, anyway.
Jerry
