From:Dave Hennessey
Subject:Wanted: a '989 Voltage Regulator Date:Wed Jun 11 00:43:51 2014
Take a look in your stash of voltage regulators, and see if you have one that looks like this, and has "N 6V 989 XX" stamped into the right mounting foot. (XX = doesn't matter)

Or, it's in a H-D box marked: 74510-59

If you do, I want to buy it!

It's not a Hummer part, it fits magneto Sportsters 1959-1965

The article below is written about K-models and Sportsters, but it lists the regulators used in the Hummer-series.