The "short shaft" water pump is just one that's had its hub pressed back to supposedly align with the single groove in the older balancer. Take the back plate off the pump and push the hub back carefully until the grooves line up. Then cut a little more off the pump shaft if necessary. A much better idea would be to get the pump relocation plate Pre 68 Dave sells and install a 216 style water pump. Then the vertical position of the fan will be right as well.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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