V8 Water Pump Comparisons (For pre-1987s)
 
 
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Buick V6
Buick/Olds 215
Buick 300 or 340

 
Rover 3500 (#1) Rover 3500 (#2) Rover 3.5 Sd1 Vitesse
Morgan Plus 8 Ready

All of these pumps will fit the Buick/Olds/Early Rover timing cover.  Depending on your engine set up, some may be more advantageous than others.  The Buick and Olds pump have an outlet that stick straight out and will interfere with a Rover alternator cradle.  The V6 pump is too long to line up the WP pulley with the crank pulley.  Perhaps the best choice is the Buick 300 or 340 pump.  Its pulley mount is shorter than the rest, providing more radiator clearance, and it is still available new for $35 at any local parts store.  Specify '67 Buick Skylark with the 300 engine as the application and make sure it is aluminum, as there are cast iron ones.  The pulley to use to get the belt to line up is #9604 at any speed shop.  $25.

It is a single groove chrome pulley used on '69-'85 GM applications with V8 engines.  Its mounting holes are larger so a new set will have to be drilled to get it to mount on the pump.  Because it is a shorter pump, an engine driven cooling fan is more easily fit behind the radiator.