All '73 and up small blocks used a long water pump. You can use that pump, but you will need to change the mounting bracket and pulley to a bracket and pulley for a short water pump. All trucks '72 and earlier and cars '68 and earlier used short water pumps. If you can not find factory brackets and a pulley, there are a couple aftermarket suppliers that make quality parts.
http://www.alangrovecomponents.com
http://www.cvfracing.com