Well, Jim Carter only has a few mistakes in that listing.

"1937-1962 Water Pump Short Shaft Style Chevrolet Pickup Truck"
1937-1962??

It works in/on a "1955-1962, 235 or 261 engine" that is to be installed in a "1937-1955 Chevrolet truck"

"Includes proper narrow 3/8 inch groove pulley to match that on the engine harmonic balancer."
The 3/8 in pulley was used from 1953-1955st older style engines.
The pre-1953 216/235 engines used 5/8" pulleys.

You can use a 3/8" belt in the 37-52 216/235s, but it will ride low in an original 37-52 5/8" groove harmonic balancer and it would ride low in an original 37-52 generator pulley.
Jim Carter sells a 3/8" belt for this water pump and application.

Jim Carter says this fan blade will work with his short shaft water pump.
This will/should have no clearance problems in the older trucks, but the fan blade will not be located in the optimal-cooling location in the older trucks.

Obviously, there is no need for Dave's water pump relocation plate with this water pump.