Speedo

I did it for the exact same reason. I rebuilt my car all new everything! I wanted zeros also. It was easy to do on my 71 scamp, but I dont know how to do it on your style. It should be fairly easy to figure out though. Like stated crack it open and investigate, it shouldnt be to hard.

Oh and really its no different than if you bought aftermarket gauges and installed them? They start at zero so I see nothing wrong with rolling back the odometer. Especially if you just installed all new drive train and parts like myself. Now if you are doing to with the intent to defraud someone to get more for your car that is a different story. Just saying.