I think that's a Hercules motor. You don't have to remove the counterweight. It's not one of the easier ones. One thing I've noticed is the new pumps have a thicker area on the side/edge of the cast housing that doesn't let the pump sit down tight on the block because it interferes with a bracket or something on the front of the block also. You have to take a grinder and take a little metal off there. Hold the new pump in place and you will see what I mean, it just barely interferes. I don't know what's up with that, but the ones I've done have had that problem with the new pumps (Cats and Daewoo)