I have a 351W with a March Pulley setup P/N 30380 for the driver side lower radiator hose and standard rotation water pump. Everything fit pretty well. Misalignment on the alternator pulley was ~0.100" which was adjusted with a spacer (washer) on the 7/16" alternator bolt between the head and spacer. Misalignment on the water pump pulley was about ~0.060" which I adjusted with a generic w/p spacer that was 0.062". The alternator and w/p pulley's both needed to come away from the engine. After alignment, the misalignment was only about 0.002" which is pretty good considering that there is some variance in the harmonic balancer and water pumps.
I measured the misalignment by putting a straight edge on the crank pulley (across both sides), measuring the distance to the belt on the crank pulley. Then measured the distance from the straight edge to the belt on the alternator and w/p pulleys and subtracted the distance measured on the crank pulley.
BTW, I'm using an inline radiator cap and no Harrison tank. The March pulleys are a bit pricey (~$400)
Here's pix of the setup.
Russ