Replacement Odometer in Diesel Vehicle

Hey everyone, I'm looking for some advice on what to do about this situation I'm in.

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I recently purchased myself a 30 year old Nissan Navara 4wd and the odometer didn't tick over, what I did was replace the speedo part in the cluster with one that now works fine, my only issue is that the ks on the old are ~400,000 and the new one only has ~224,000, I know I'm able to fill out some form through the NZTA and let them know, but i believe that form is only really designed for Hubo changes. I'm considering trying to find an old scrap car with the odo matching close enough to the original in order to just not have to fill out a form.

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Does anyone have anything to add?

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TLDR

Changed my cluster, now the odometer is inaccurate, and I need to notify NZTA, OR find new cluster with closer Ks on the clock.