speedo corrector kit

Hi guys, I have a vn series 2 commodore and i converted it to manual using a vr gearbox and that , runs fine, but the speedo and reverse lights won't work. Anyone have any suggestions or come across this before? should i get a speedo corrector kit?

for those that are running shorter diff ratios or have fitted larger wheels and the speedo is reading a little faster (or sometimes a lot depending on gears used) here is a simple way to fix this problem parts required: speedo corrector kit available from Jaycar for about $60 pic 1 UB3 jiffy...