Look, man, when I suggested the Blue Sea products fuse panel, it wasn't so you could turn the GP into a freakin' boat!
🤣 🤣
This suggests that any aftermarket electric speedo will work. Usually they count the pulses in a specific distance. I've used mile markers on the highway; do they have KM markers in Canadia? You stop next to one, engage the 'set/calibration' mode, drive to the next marker, and set it. The speedo counts the pulses given in that distance, and calibrates accordingly. A factory GM speedo is going to be calibrated to GM VSSes, so I don't know if it can be programmed to use this within reasonable cost effectivity.